UPDATED: Dana Hills High School on Lock Down After Empty Gun Case Found in Parking Lot

UPDATE at 3:58 p.m.: Students were released from the campus after 3:30 p.m. Lt. Jeff Hallock of the Orange County Sheriff's Department said nothing suspicious was found and no suspects were detained. The gun case was found on the ground in the parking lot at Dana Hills and someone had brought it into the school office before deputies arrived on campus.

Original story:

The discovery of an empty carrying case for a rifle or shotgun in a campus parking lot prompted a lockdown and room-to-room search of Dana Hills High School today, but no weapon was immediately found.

The search began shortly before noon when the case was found outside the school at 3333 Golden Lantern St., according to Orange County sheriff's Lt. Jeff Hallock.

Students were forced to remain sheltered in place inside classrooms at the school, while sheriff's deputies and a SWAT team combed through the campus.

Dozens of concerned parents flocked to the school in hopes of picking up their children, some of whom were communicating via text message with people outside the campus. Some parents told KCAL9 the students' backpacks were being searched, and some students were being held in darkened rooms.

One parent, Stephanie Andrews, told the station that according to her son, some students were urinating in classroom sinks because they were not being allowed out of their classrooms.

"It is scary to them to see guard dogs and SWAT team members going up and down their school and just in light of recent incidences, not knowing what could happen -- it's very scary to them," she said.

Hallock stressed that no weapon had been found at the campus, but the search was likely to last for the bulk of the afternoon.

"We're taking it seriously and as a precaution conducting a very thorough search of the school," he told KCAL9 at the scene.