COLUMBINE, Col. (AP) - UPDATE: Students are leaving classes after tightened security at Columbine High School and over 20 other Denver-area high schools after a lockdown caused by a possible threat.
Students wearing backpacks came out the main door at Columbine on Tuesday afternoon, soon after school officials announced that students in all the schools put on lockdown were safe and would be dismissed at their normal times. The students walked to crosswalks and buses parked near the entrance.
Officials said after school activities will be held at all schools except Columbine, but didn't explain why.
A spokesman for the Jefferson County Sheriff's Office, Mike Taplin, said the lockdowns involved an FBI investigation but he couldn't provide any details. The sheriff's office previously said the lockdowns were prompted by an investigation into what appeared to be a credible threat possibly involving the schools
The lockdowns come just days before the 20th anniversary of a mass shooting at the school that killed 12 students and a teacher.
ORIGINAL: Columbine High School and about a dozen other schools are on lockdown as law enforcement says it is investigating what appears to be a credible threat possibly involving the schools.
School officials say the doors were locked but classes were continuing Tuesday at Columbine and two other nearby schools and at other schools farther away in the district.
The Jefferson County Sheriff's Office said deputies were posted at the schools involved.
The lockdown comes just days before the 20th anniversary of a mass shooting at the school that killed 12 students and a teacher. There was no immediate indication whether Tuesday's lockdown has any connection to the anniversary.