The latest revelations about the teenage killers Dylan Klebold and Eric Harris came as more funerals of their victims took place, including that of the teacher hailed as a hero for his role in directing students to safety.

From the boy's diaries and the taunts they shouted as they attacked fellow students, the pair apparently carried out the shootings in revenge for insults from classmates who they said had made them outcasts.

Diary was found at Eric Harris's house

But the authorities now say the diaries indicate the two teenagers planned even more destruction, both within the town and beyond.

They wanted to kill 500 people, hijack a plane and crash it into New York City, Jefferson County Sherrif department's spokesman, Steve Davis, told reporters.

Mr Davis said the diary had been found in Harris' bedroom alongside bomb- making materials and other weapons.

It also notes how the massacre had been a year in the planning and timed to coincide with Hitler's birthday.

Amazed at the firepower Harris and Klebold had managed to accumulate, investigators say they suspect that others may have been involved or at least known what they were planning.

Police questioned Klebold's 18-year-old girlfriend about whether she purchased two of the firearms used in the shootings.

Officials said the woman had not been named as a suspect and no arrests were imminent.

Funeral of a hero

Many pupils say Mr Sanders' actions saved their lives

William "Dave" Sanders, a computer teacher and popular sports coach at the school, was gunned down as two students shot their way through the school building before finally turning their guns on themselves.

Terrified pupils later said many of them owed their lives to Mr Sanders' quick thinking.

More than 2,000 people crowded into and around Littleton's Trinity Christian Center for Monday's funeral. A memorial service held in the town on Sunday was attended by more than 70,000 mourners including US Vice-President Al Gore.

US Vice-President Al Gore pledges to replace the culture of violence

"He was and always will be a hero in my heart," his niece, Kim, told mourners.

Mourners gathered at three other services on Monday. About 2,000 people attended the funeral of Cassie Bernall, 17, the girl who answered "yes" when asked by one of the gunmen if she believed in God. The gunman then shot her dead.

"Cassie's response does not surprise us," the family said in a statement released at the funeral. "Her life was rightly centered around our lord Jesus."

Friends wrote messages of sorrow on Cassie Bernall's coffin

About 700 people heard Lauren Townsend described as "remarkable girl" by her family.

Miss Townsend, 18, was captain of the girls' volleyball team and an honor student.

Daniel Rohrbough, 15, was killed while holding a door open for fellow students fleeing the gunmen. His funeral was held later on Monday.

Wall Street tribute

The BBC's Rob Watson: Investigators are increasingly convinced the boys may have had accomplices

Earlier, traders on Wall Street broke off from the start of their normally frenetic business for a minute's silence in memory of the victims.

It has emerged that the parents on of the gunmen, 17-year old Dylan Klebold, sensed "tension" in their son several days before the attack.

A signed basketball was one of many tributes to a popular sports coach

Reports in Monday's New York Times quote family pastor, the Reverend Don Marxhausen, as saying Dylan's mother, Susan, told him that she suspected something had been bothering her son as he left for school on the morning of the attack.

"The goodbye had an edge to it," she told the pastor. "She thought, maybe he's in a bad mood. Maybe he's got a test today or something."