The lockdown at Arvada K-8 was lifted late Friday evening.
Law enforcement and Jeffco Public Schools Security responded to the school at 5751 Balsam Street.around 3:15 p.m.
"The school resource officer identified a threat outside the school and directed a lockdown to keep students and staff safe," said Diana Wilson who is the Chief Communications Officer with
Jeffco Public Schools.
The district was telling parents it would provide additional details as it learned about them.
It was asking parents who are at the school to pickup children to remain in their vehicles until the situation was resolved.
"Students will be cleared classroom by classroom after law enforcement determines it is safe to leave the building," said Wilson.
Arvada police tweeted around 3:30 p.m. that they were doing a controlled release of the school starting with students who ride the bus.
Shortly before 5 p.m. the district posted a message that all students must be picked up by a parent or guardian because of the threat. To get their child they must show a photo ID.
Around 5:45 p.m. the police department lifted the lockout.
It was not clear what the threat outside the school involved.