Classes were canceled and final exams delayed at Columbine High School after a student received a threat in an Internet chat room.
The threat was sent by someone outside Colorado to a 16-year-old Columbine student and warned her not to go to school today, said Jefferson County sheriff's spokesman Steve Davis.
"I need to finish what begun and if you do I don't want your blood on my hands," it read in part, Davis said. Agents were trying to find the sender, who used the screen name "Soup 81" to post the threat in an America Online chat room, Davis said.
"In the interest of the safety and emotional well-being of our community, we canceled classes," school district spokesman Rick Kaufman said.
Holiday break at the 1,980-student school started two days early, and final exams will be made up in January.
"It's a really bad joke," senior Dan Goin said. "Now we're going to have to study over the break. But you never know, they may have saved all our lives today."
Some parents have said that sheriff's officials ignored Internet threats that foreshadowed the April 20 shooting rampage at the suburban Denver school. Twelve students and a teacher were killed by teenage gunmen Dylan Klebold and Eric Harris, who then committed suicide.
The family of the student who received the threat Wednesday night immediately contacted the sheriff's department and school security, Kaufman said.
Authorities "swept the building inside and out" but found nothing, said district spokeswoman Marilyn Saltzman.
The district planned to go ahead with a Christmas concert tonight.
In October, many students stayed away from school for one day after a student threatened to "finish the job" Klebold and Harris started. That student, whose name was not released, pleaded guilty Monday and was ordered to perform community service.