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LITTLETON, Colorado (CNN) -- A female friend of one of the two dead students blamed in last week's massacre at Columbine High School provided at least one of the guns found at the crime scene, investigators said Monday.

But there is not enough evidence for her to be considered a suspect in plotting the attack, authorities said.

Jefferson County Sheriff's Department spokesman Steve Davis said the unidentified 18-year-old woman was questioned and released, but likely will face further questioning.

The federal Bureau of Alcohol, Tobacco and Firearms (ATF) traced at least one of the four weapons used by Dylan Klebold, 17, and Eric Harris, 18, to Klebold's girlfriend, who knew both boys, said Davis.

"She just thought, from what we had, that she was being a friend," said Chief Deputy District Attorney Mark Pautler. "They wanted to get these weapons, they were underage, they probably went to a gun show and purchased them.

"But we don't have any information at this time that she had knowledge concerning the ultimate use of those weapons."

The equipment that Harris and Klebold used to make more than 30 explosive devices that they had on the day of the attack came from other friends, officials said.

Authorities remain convinced that the amount of ammunition and bombs used in the attack was too much for the two dead gunmen to have carried by themselves into the building.

The FBI is trying to enhance images on a videotape from a surveillance camera in the school cafeteria where a large propane bomb was discovered. They hope it will help them determine whether the killers had accomplices.

Bomb squads and dogs continued their search Monday for more explosives.

Harris, left, and Klebold made more than 30 explosive devices

Davis said District Attorney Dave Thomas reserves the right to charge the girl, the suspects' parents or anyone else as accessories, if it's determined they knew about the plot and did nothing to stop the attack that left the gunmen, 12 other students and a teacher dead.

Prosecutors also said several people who have been questioned about the massacre have hired attorneys.

Victim's family contacts attorney

Also Monday, Geoffrey Fieger, the Michigan attorney who has represented Dr. Jack Kevorkian, said that the family of one of the victims had contacted him about the possibility of representing them.

Fieger said Isaiah Shoels' family talked to him about a possible lawsuit because they had reported prior to the killings that their son was being taunted and threatened with violence by the shooters' clique.

Their complaints were echoed by another family that said they had filed reports with the Jefferson County Sheriff's office about threats made by Harris.

Randy Brown said he complained to the sheriff's department that a death threat against his son, Brooks, had been posted on Harris' computer Web page.

"I am the law. If you don't like it, you die," a passage from the Web site said, according to Randy Brown. "If I don't like you or what you do, you die."

"All I want to do is kill and injure as many of you as I can, especially a few people like -- he mentions my son's name here,' Brown told Denver station KCNC-TV.

"The police department was handed this on a silver platter and did nothing," Judy Brown, the boy's mother said. "That's how I feel."

Jefferson County Sheriff's spokesman Steve Davis declined to comment on Brown's assertions.

On the day of the shooting, Harris walked by his classmate Brooks standing outside, told him to go home, and then entered the cafeteria and opened fire, Brown said. "We were pretty lucky there," Randy Brown said. "My other son (Aaron) was shot at several times by Eric while he was running up the stairs and he missed him."

Students hug during a visit to a makeshift memorial in a park near Columbine High School

Diary exposes blueprint for massacre

Harris and Klebold had been planning the attack for at least a year, police said, quoting a diary found at Harris' home.

The diary was described as a rambling diatribe of hatred with a blueprint for the assault that established a goal of destroying the school with bombs and killing at least 500 people.

According to the diary, the gunmen even scheduled downtime, or time to "chill," for the morning of the attack. Police said that, in fact, the two went bowling before they headed for school to launch the attack.

The diary also offered options for escape that included hijacking a plane, loading it with explosives, then crashing it into New York City, or moving to a desert island, police said.

A pastor to the Klebold family said the family was in shock and never saw any sign that the youth was troubled.

"This is beyond a nightmare. Their world is devastated," the Rev Don Marxhausen, a Lutheran minister said. "This wasn't their kid. This is not the Dylan they knew. Susan and Thomas Klebold can't reconcile it at all. ... This was a boy who used to clean up poor neighborhoods."

• Toxicology reports on the two killers showed no traces of alcohol or drugs, the Jefferson County Coroner's office said Monday.
  
  
• A student wounded in the attack, Valeen Schnurr, 18, was released Monday from Swedish Medical Center where she had undergone surgery for multiple gunshot and shrapnel wounds, including nine to the chest.
  
  
• Another hospitalized student, Casey Ruegsegger, 17, underwent surgery at St. Luke's Presbyterian Hospital for multiple gunshot wounds to her shoulder and hand.
  
  
• President Clinton plans to propose new legislation that includes requiring instant background checks for the purchase of explosives and for the purchase of guns at gun shows, according to White House aides. Current gun control laws exempt gun shows.
  

Correspondents Tony Clark and Martin Savidge, The Associated Press and Reuters contributed to this report.