Mental patients who disappeared in the aftermath of the Kosovo conflict may have fallen victim to organ-traffickers in neighboring Albania, Serb prosecutors said Thursday.

Serbia's war crimes prosecutor spokesman Bruno Vekaric told The Associated Press that authorities have evidence as part of an investigation into the fate of more than 300 Serbs allegedly abducted by ethnic Albanian rebels during and after the 1998-99 Kosovo war.

Vekaric said the disappearance of 40 people in 2001 from a mental hospital in the Kosovo town of Stimlje may have been linked to the alleged ring. Vekaric alleged the patients were transported to Albania in vans and have not been seen since.

"The reliable evidence fits the picture that something gruesome was going on in Albania," Vekaric said.

However, the U.N. War Crimes Tribunal investigated in 2002 and 2003, and concluded there was insufficient evidence to prove the ring existed.

Memli Krasniqi, a spokesman for the Kosovo government, said the claims were "mere speculation from Belgrade."

A spokesman for the Kosovo police said that Serbian authorities should give any evidence they have to the international prosecutor.

Vekaric's remarks seemed intended to pressure Albania to revive an investigation into the alleged ring. Albania's top prosecutor has refused to reopen the investigation.

In "The Hunt: War Criminals and Me," published earlier this year, former chief U.N. war crimes prosecutor Carla Del Ponte wrote that about 300 people were kidnapped and transported to Albania, where they disappeared. There were reports that some were victims of an organ harvesting operation, Del Ponte wrote. She did not identify the source of those reports.

Thousands were killed as Serb security troops cracked down on Kosovo Albanian separatists. The conflict ended after NATO bombed Serbia in 1999.

Kosovo declared independence from Serbia in February, a declaration Serbia does not accept.