LONDON (AP) — Doctors who treated poisoned ex-spy Sergei Skripal and his daughter Yulia say they don't know what their long-term prognosis is.

The pair were found unconscious in the English city of Salisbury March 4 after being exposed to a nerve agent known as Novichok. They spent weeks comatose in critical condition but have now been discharged.

Salisbury District Hospital medical director Christine Blanshard says "we don't know" what the long-term effects of the poisoning will be.

Blanshard told the BBC in an interview broadcast Tuesday that "we have a total world experience of treating three patients for the effects of Novichok poisoning" — the Skripals and a police officer who helped treat them.

Britain says Russia was behind the poisoning with the military-grade nerve agent. Moscow strongly denies the allegation.