The Syrian regime has agreed to dismantle its arsenal of chemical agents but may now have the ability to produce biological weapons, the U.S. intelligence chief warned senators Wednesday.

“We judge that some elements of Syria’s biological warfare program might have advanced beyond the research and development stage and might be capable of limited agent production, based on the duration of its longstanding program,” James Clapper, director of national intelligence, said in a written statement presented to the Senate Intelligence Committee.

Clapper offered no further details but it was the first time officials had stated publicly that America’s spy agencies believed Syria had made significant strides in its biological weapons program.