Los Angeles, Apr 17 (AFP) Nearly two decades after the infamous Columbine High School massacre, officials in the US state of Colorado were on alert Tuesday after learning of threats from a woman police say is "armed and considered to be extremely dangerous."

The FBI and local police identified the suspect as Sol Pais, 18, and more than 20 schools in the Denver metropolitan area increased security measures following reports of the threat.

"Due to a credible threat to schools by an individual identified by the FBI, the Department of Public Safety recommends all schools in the Denver metro area conduct a lockout and controlled release immediately," the Colorado Department of Education said.

The Jefferson County sheriff's office said on their social media accounts that Pais "traveled to Colorado and made threats in the Denver metropolitan area. She is armed and considered to be extremely dangerous."

The postings included two photos of the suspect, described by the FBI as "a white female... approximately 5'5" in height, with brown hair."

Pais is "obsessed" with the April 20, 1999 massacre in Columbine High School in Littleton, a suburb of Denver, when Eric Harris and Dylan Klebold shot dead 12 fellow students and a teacher before killing themselves, the Denver Post reported.

The sheriff's department said that the students were safe and that security had increased at the area schools, but said little about Pais.

"Because this is an active and ongoing investigation we cannot release further info about where Sol Pais is from, how long she has been here & the nature of the threat. That could compromise the investigation," the sheriff's department tweeted. (AFP)

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