Syria Likely Has Over 100 Chemical Weapons Sites, Inspectors Say

More than 100 chemical weapons sites are suspected to remain in Syria, left behind after the fall of the longtime president, Bashar al-Assad, according to the leading international organization that tracks these weapons.

That number is the first estimate of its kind as the group, the Organization for the Prohibition of Chemical Weapons, seeks to enter Syria to assess what remains of Mr. al-Assad’s notorious military program. The figure is far higher than any that Mr. al-Assad has ever acknowledged.

The sites are suspected to have been involved in the research, manufacturing and storage of chemical weapons. Mr. al-Assad used weapons like sarin and chlorine gas against rebel fighters and Syrian civilians during more than a decade of civil war.

The number of sites, and whether they are secured, has been a mystery since rebels toppled Mr. al-Assad last year. Now, the chemicals represent a major test for the caretaker government, which is led by the group Hayat Tahrir al-Sham. The group is designated as a terrorist organization by the United States, but it has renounced its links to Al Qaeda.

The stakes are high because of how deadly the weapons are, particularly when used in densely populated areas. Sarin, a nerve agent, can kill within minutes. Chlorine and mustard gas, weapons made infamous in World War I, burn the eyes and skin and fill the lungs with fluid, seemingly drowning people on land.

Experts are concerned about the potential for militant groups to gain access to poorly secured chemical weapons facilities.

In a surprise visit in March to the global chemical weapons watchdog headquarters at The Hague, Syria’s foreign minister said that the government would “destroy any remains of the chemical weapons program developed under the Assad regime” and comply with international law.

Experts are cautiously optimistic about the government’s sincerity. The current government allowed a team from the watchdog to enter the country this year to begin work documenting the sites, according to people with knowledge of the trip.

But Syria remains in a precarious spot, as violence erupted in the coastal region in recent weeks between government forces and groups aligned with Mr. al-Assad. And despite promises, the new government has not yet appointed an ambassador to the watchdog — a key first step that is seen as a sign of a country’s commitment. Syria’s defense ministry declined to answer written questions about the weapons, saying without elaboration that the questions were not under its purview.

In the early years of the civil war, Mr. al-Assad’s government declared the locations of 27 sites to the Organization for the Prohibition of Chemical Weapons, or O.P.C.W., which sent inspectors to visit and shut them down. But Mr. al-Assad continued to use chemical weapons until at least 2018, and research showed that his government kept importing essential precursor chemicals.

The current estimate of more than 100 sites comes from the watchdog and has been circulated recently among experts and international nonproliferation analysts. The organization said it had arrived at the number based on outside researchers, nonprofit groups and intelligence shared by its member countries.

Some sites are probably hidden in caves or other places that are tough to find using satellite images, according to researchers, former organization staff members and other experts. That increases the likelihood that some weapons are not secured.

“There are many locations that we don’t know about because the old regime was lying to the O.P.C.W.,” said Raed al-Saleh, the leader of the Syria Civil Defense, also known as the White Helmets, a volunteer group that says it is working with the government to try to dismantle chemical weapons sites.

Nidal Shikhani, who leads the Chemical Violations Documentation Center of Syria and has worked with the Organization for the Prohibition of Chemical Weapons for years, said his group had identified dozens of new locations that could be chemical weapons stockpiles or former research sites based on interviews with Syrian government scientists living in Europe.

Finding and taking control of these sites is important for reasons beyond security. Inspectors also want to collect evidence for their investigations into Mr. al-Assad’s repeated use of chemical weapons. International observers, independent researchers and Syrian humanitarian groups have documented dozens of attacks, with thousands of people, including children among the victims. The most notorious was a 2013 sarin gas assault on the area of Ghouta, a suburb of Damascus, the capital.

Last year, Israel launched airstrikes on several Syrian regime facilities where chemical weapons were known to have been held. But it is unclear whether those strikes destroyed chemical weapons.

Mr. Shikhani and others said they worried that the strikes merely created environmental contamination and destroyed evidence. International groups hope that chemical evidence will answer key questions about the Assad government’s research and help with international prosecutions.

“The Israeli attacks that happened right after the fall of Assad are probably likely to not have put a dent in some of this, and potentially also obscured efforts toward accountability,” said Natasha Hall, a senior fellow with the Center for Strategic and International Studies in Washington.

Sarin gas is prohibited under international law. The rules are murkier for other chemicals. Chlorine gas, for instance, can be created using common household cleaning products. That makes it nearly impossible to regulate the sale of precursors.

Syria’s chemical weapons program began in the 1970s with the help of hundreds of government scientists, many of whom were trained in Germany and other parts of Europe, according to a Syrian former senior government chemist who spoke on the condition of anonymity out of fear of retribution.

The scientist worked in the chemical weapons division of the military’s Scientific Studies and Research Center. That center, which is under international sanctions, worked on conventional, chemical and nuclear arms.

Many scientists, he and others said, fled the country during the war, but others remain in Syria. The United States has imposed sanctions on more than 300 people and entities in connection with Syria’s chemical weapons program.

Despite the assurances of the new government, weapons inspectors are tempering their optimism. They have heard such assurances in Syria before.

Syria first agreed to get rid of chemical weapons more than a decade ago. But as inspectors conducted their work, they became convinced that Mr. al-Assad had no intention of revealing complete information about his stockpiles. Former staff members say they were perpetually hamstrung by the government.

In one episode in 2014, inspectors and Syrian staff members were investigating a potential site when a car in their convoy struck a roadside bomb. Two Syrians who were in the convoy blamed the government for misleading them and assuring them the route was safe. Other staff members recalled being constantly afraid that the government was eavesdropping on their conversations or spying them.

Mr. al-Assad’s government also covered up attacks in which it used sarin and chlorine gas on its own people.

In the town of Zamalka, near Damascus, headstones mark the names of many residents killed during the war, and the dates of their death. On the other side of the cemetery sits a mound of dirt, piled high to the ground, its significance unmarked.

It was there, a local official said, that the town had buried the local men, women and children who were killed in a 2013 suspected chemical weapons attack. When Mr. al-Assad’s government recaptured the town in 2017, the official said, the government removed the headstones and covered up the gravesites.