DAMASCUS, Syria (AP) — A convoy of chemical weapons inspectors came under attack Tuesday while traveling to the site of a suspected chlorine gas attack in Syria, but all staff members were safe, the international watchdog agency said.

The Organization for the Prohibition of Chemical Weapons has been working with the United Nations to oversee the destruction of the Syrian government’s stockpiles since September 2013, when President Bashar Assad’s administration acknowledged it has chemical weapons and agreed to give them up to avoid the threat of U.S. military strikes.

Syria has since destroyed or handed over more than 90 percent of the weapons and toxic chemicals it has formally declared. Its sole remaining declared stockpile has been packaged for shipment out of the country to meet a June 30 deadline for destruction.

However, last month allegations surfaced that chlorine gas has been used as a weapon in fighting between the government and rebels. Chlorine is not banned under chemical weapons conventions, and it was not part of Syria’s disclosures. However, using any toxic material in warfare violates chemical weapons treaties and international law.

The circumstances of Tuesday’s attack were unclear. Syria’s Foreign Ministry initially reported that 11 people, including six members of a U.N. fact-finding mission and their Syrian drivers, had been abducted by rebels fighting to topple Assad’s regime. But the OPCW issued a statement shortly afterward saying a convoy had come under attack but “all team members are safe and well and are travelling back to the operating base.”

Opposition activists could not immediately be reached for comment.

The Syrian Foreign Ministry said the convoy, which consisted of four vehicles, was heading toward the rebel-held town of Kfar Zeita where activists and Human Rights Watch reported gas attacks on April 11 and April 18 that killed two people.

It said the government had agreed to a daylong cease-fire in the town in the central province of Hama “to facilitate the work of this mission.” As the team reached the nearby government-controlled village of Taibet al-Imam, the government said it was unable to provide protection beyond that point but the team decided to continue without Syrian security forces, according to the statement.

A roadside bomb then hit one of the team’s vehicles, forcing the passengers to move to another car and turn back toward Taibet al-Imam, the ministry said. The ministry said only one vehicle arrived in the village, which is under government control, a fact that might have caused Damascus to issue the statement saying the rest had been abducted.

A doctor in Kfar Zeita who identified himself as Abdullah Darwish said the team had been expected to arrive in the village on Tuesday and medical officials had prepared for them documents as well as a number of people who suffered during the alleged chlorine attack. But the main rebel group the Free Syrian Army later said the inspection team wouldn’t be coming, Darwish told The Associated Press via Skype.

The OPCW Director-General Ambassador Ahmet Uzumcu expressed concern about the attack, repeating his call to all parties for cooperation with the mission.

“Our inspectors are in Syria to establish the facts in relation to persistent allegations of chlorine gas attacks,” Uzumcu said. “Their safety is our primary concern, and it is imperative that all parties to the conflict grant them safe and secure access.”

The Geneva-based OPCW, which monitors the implementation of the Chemical Weapons Convention and oversees the destruction of Syria’s chemical weapons, had sent a team to Damascus this month to investigate claims that chlorine has been used in Hama. The U.N. Security Council authorized the OPCW to oversee a fact-finding investigation into the alleged gas attacks.

The Syrian government has agreed to cooperate with the inspectors and their U.N. security detachment in the parts of the country it controls.

In August, a U.N. team that was trying to reach a Damascus suburb following a chemical weapons attack came under fire. Both the government and the opposition blamed each other for that attack. No one was hurt in the attack and the inspectors eventually arrived in Moadamiyeh, a western suburb of Damascus.

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Sterling reported from Amsterdam.