Developing: Colorado School Lockdown

A high school was locked down Thursday amid unconfirmed reports that two masked men were seen entering the building.

Officers from various law enforcement agencies could be seen outside Boulder High School, and the entrances to the parking lot and the building were blocked off.

Boulder Police spokeswoman Julie Brooks confirmed that the school was locked down and that authorities were on the scene, but she released no further details. She would not confirm a report by KOA Radio that a school staff member had seen masked men entering the building.

Hopefully this was just a misunderstanding and that the staff member was mistaken in what they had seen, but law enforcement is not taking any chances.

UPDATE:
Still no new news on the situation, but I found an article showing that the school had been subject to threats last month in the aftermath of the Virginia Tech murder spree:

Seventy percent of Boulder High School students were absent Thursday, in part because of graffiti found in March in a bathroom saying, "Everybody dies April 19."

Right now, there's no way to know if there's any connection or whether this is simply a wild goose chase.

UPDATE:
Classes were cancelled for the day, but nothing out of the ordinary was found in a sweep of the school's grounds.