GOLDEN, Colo. (AP) _ Investigators are focusing on three camouflaged teen-agers detained shortly after the Columbine High School massacre as possible co-conspirators who may have planned to join the carnage, Jefferson County Sheriff John P. Stone said Tuesday.

``They were in combat fatigues. They said they heard it on the radio. Well, it wasn't on the radio at that time,'' Stone told The Associated Press.

For the first time, Stone laid out the timeline for the attack and also disclosed that a school surveillance camera captured the attack in the cafeteria. Stone's department is leading the investigation into the April 20 shootings in Littleton.

Stone declined to name the teens, who have been questioned but not formally named as suspects.

``They are subjects of our investigation,'' Stone said. ``We'll be going back to talk to these kids.''

While the drama unfolded on national television, the three young men in dark jackets were stopped by deputies. They were frisked and taken off for interrogation. The men carried no weapons.

Inside the school, Eric Harris, 18, and Dylan Klebold, 17, killed 12 classmates and a teacher before turning their guns on themselves.

The three young men, who Stone said knew the gunmen and had previously been associated with their ``Trenchcoat Mafia,'' have maintained their innocence. Investigators tested them for gun residue after the shootings and found no evidence that they had fired guns.

Although Stone called the three among his ``best leads,'' sheriff's spokesman Jim Parr told other media outlets late Tuesday that investigators had questioned the three men and cleared them. Parr could not be reached to explain his comment.

District Attorney Dave Thomas, reached late Tuesday, told the AP that investigators have been interested in the three men since the shooting began.

``They're among a group of people who we think have information,'' Thomas said. He said that Stone may have stronger suspicions about the three than others involved in the investigation.

``Are they people we believe have information about this? You bet,'' Thomas said. ``We have said that since day one.''

All three teens claimed to have heard of the massacre on the radio _ and were able to name the gunmen _ before the names had been released, Stone said. One of them had been expelled from Columbine High School, he said.

The Denver Rocky Mountain News identified the three men who were questioned as Matthew Christianson, Matt Akard and Jim Branetti.

``We were just three punks with a lot of curiosity,'' Christianson said in Monday's editions.

A woman who answered a call Tuesday night to Akard's home, told the AP she had no comment.

``You have absolutely no interest in benefiting my son and I have nothing to say to you,'' the woman said before hanging up. Efforts to locate Christianson and Branetti were unsuccessful.

All three wore black jackets with combat-style boots when they were taken into custody.

``That's the scaredest I've ever been,'' Christianson said. He said they didn't know Klebold and Harris.

Stone said the two gunmen initially tried to escape through three separate exits, and killed themselves only after being turned back by deputies' gunfire each time. Stone said a diary seized at the home of one of the killers indicated the gunmen planned to fly to Mexico or another country if they could escape, and kill themselves if they couldn't get out.

``They wanted to go to Mexico, or find an island, some place to get away from America, or maybe come out and hijack and crash an airplane in New York City,'' he said, giving details from a sheaf of papers investigators have characterized as a diary.

Stone said a school surveillance camera captured ``the entire carnage'' in the cafeteria, where Klebold and Harris hurled homemade bombs and opened fire on terrified students. Authorities have sent the tapes to an FBI lab in Quantico, Va., to be analyzed frame-by-frame. Authorities previously have not said whether the tapes contained any useful images.

After the cafeteria attack, the two gunmen ran upstairs to the library where they caught many students studying during their lunch hour. They then ran into the administration offices.

``They shot the hell out of the administration office, but apparently there was no one in there,'' Stone said.

Stone's disclosure came one week after the rampage. On Tuesday, silence fell across the Denver area and church bells tolled 15 times _ one for each victim and the two gunmen. Televisions and radios fell silent for one minute at 11:21 a.m. After the tolling, the bells rang out in joyous tones.

Funerals for three more victims _ Matthew Kechter and Kyle Velasquez, both 16, and Corey DePooter, 17 _ were held. The Velasquez services drew 800 mourners, including Gov. Bill Owens.

Investigators have questioned Klebold's 18-year-old girlfriend, who bought at least two weapons used by Klebold and Harris. Investigators want to know whether she knew how the guns were to be used.

Meanwhile, an employee of a local hardware store said he saw Harris purchase several barbecue containers of propane and bags of nails, screws and wires.

Four guns were found in the school. On Tuesday, authorities said they had discovered 50 bombs, ranging from small pipe bombs to at least one large incendiary device rigged with barbecue propane tank. If they had been detonated, investigators say they might have blown up the school, killing hundreds.

Investigators said Robyn K. Anderson bought at least two of the weapons _ a rifle and a semiautomatic TEC DC-9 handgun _ at a Denver-area gun show in the fall. Miss Anderson has not been arrested, and authorities stopped short of describing her as a suspect. She has retained a lawyer and is said to be cooperating.

Generally, it is illegal to give a minor a pistol, and illegal to give anyone a gun with the knowledge that it will be used in a crime.

Columbine teachers returned to work Tuesday _ not at the heavily damaged high school, but a few miles away at Chatfield High. Columbine students will return to classes on Monday _ also at Chatfield.