KLJUC, Bosnia-Herzegovina (AP) _ Fifty feet straight down, it is dark and wet and the cave floor is full of bodies. Some were dumped in a sitting position, some kneeling. All are thought to be Muslims killed by Serbs.

A few miles away, a cold school gym smells of death. Other bodies, lifeless for more than four years, are lined up on the floor. Relatives seeking to end the anguish of uncertainty look for a bit of clothing or paper, watches or even pencils that they recognize.

Since last week, Bosnian officials have been excavating some of the most gruesome mass graves anyone has found so far in Bosnia.

They are located in parts of western Bosnia captured from Serbs just before fighting stopped a year ago. Survivors say the victims were rounded up by local Serbs on June 1, 1992, and shot. They say the cave at Laniste and a nearby meadow hold some of the biggest mass graves in the area.

So far, 70 bodies have been pulled from the cave and laid out on the muddy grass nearby. None have been identified.

Workers also have found two plastic bags neatly tied _ each containing a human head pierced with nails. It's not certain whose heads they were, or how many more bodies are there.

Seventy-nine bodies _ those taken to the school gym _ were unearthed from the meadow. Last week, dozens of bodies were taken from a third site, including those of women and children. A baby bottle and pacifier were found on the site.

Workers, dressed just in sweaters and trousers, are soaking wet when they come out of the cave, a natural depression 109-feet deep and about 15 feet across. They seem on the verge of collapsing.

``We're now at the 15th meter,'' said Ismet Dizdarevic, a medical worker from Bihac, to the north. ``It's terrible down there.''

``It's full of bodies, bodies are everywhere. I can't explain how hard and difficult it is.''

All sides in the Bosnian war have been accused of atrocities, but Serbs have been blamed for most of them _ including their efforts to expel Muslims from areas like this at the beginning of the war. Bosnian government officials say they believe about 1,500 people are buried in mass graves around here.

Adil Draganovic, a judge who is the Bosnian government's regional war crimes investigator, said the international war crimes tribunal had been informed of the site. But no one from the tribunal was there Wednesday.

One survivor present, who spoke on condition of anonymity, said local Muslim men ages 18-60 from surrounding villages were ordered by Serbs on June 1, 1992 to come to a local school to be issued new identity documents.

Instead, he said, about 200 men were lined up and shot. The survivor said he was only slightly wounded, overheard the plans to bury the bodies at Laniste, and escaped in the dark.

His story about how the men were gathered was corroborated by others who came to give an identity to the blackened bodies on the school gym floor.

Initial identification showed the dead were Muslim men from five nearby villages.

Asim Draganovic said he recognized the body of his brother Nijaz by the shoes. A medical team later found documents on the body to confirm it. He still was looking for another brother, Dzemo.

Saura Konjevic, 70, inspected the line of dead. She already had found two brothers, but was looking for a nephew.

Suddenly she exclaimed, ``This is Ismet's checkered shirt! I found him!''

Dr. Semira Misic was conducting an autopsy on another set of remains and confirmed to Emir Cehic that the remains were those of his brother, Mirsad. Like the others, he had been shot.

Edina Becic was kneeling over one of the few bodies left unidentified. She thought the remains were of her brother, Zikret, but couldn't be sure.

``The biggest problem is that there's no upper body, so we can't be sure,'' she said through tears. ``If only we could find the other half.''