A woman stands amid the rubble of a building that was reportedly destroyed during air strikes by the Syrian regime ally Russia, in the town of Kafranbel in the rebel-held part of the Syrian Idlib province, May 20, 2019.
A woman stands amid the rubble of a building that was reportedly destroyed during air strikes by the Syrian regime ally Russia, in the town of Kafranbel in the rebel-held part of the Syrian Idlib province, May 20, 2019.

The United States says there are signs the Bashar al-Assad regime in Syria may be using chemical weapons again and it is warning the Syrians to stop it.

The U.S. State Department said Tuesday it believes Syrian forces were behind an alleged chlorine gas attack Sunday in northwestern Syria.

A spokeswoman says officials are still gathering information about the suspected attack but said, “if the Assad regime uses chemical weapons, the United States and our allies will respond quickly and appropriately.”

She says the attack would be part of a violent campaign that violates a cease-fire protecting millions of civilians in the Idlib area, destroying health facilities, schools, homes, and refugee camps.

The United States says Syria and its Russian allies have a history of blaming chemical attacks against the rebels.

“The facts are clear: the Assad regime itself has conducted almost all verified chemical weapons attacks that have taken place in Syria ... the Assad regime’s culpability in horrific chemical weapons attacks in undeniable.”

There has been no comment from Syria on the U.S. accusation.

The U.S. has bombed Syria twice in reaction to using poisonous gas on civilians.