DANA POINT (CBSLA.com) — Dana Hills High School students were released from a four-hour lockdown Thursday after an empty rifle or shotgun carrying case was reportedly found in a campus parking lot.

Orange County Sheriff’s deputies were at the school for an unknown reason when they were made aware of the incident around 11:45 a.m.

Worried parents flooded the front entrance of the sprawling campus just after 12 noon following phone calls and emails to parents notifying them of the disturbing discovery.

“My son is texting me from inside. He’s saying that he’s fine and they’re barricaded in a room,” one parent told KCBS.

Dozens of officers and the Orange County sheriff’s SWAT team with its armored vehicle rolled onto campus and began an all-out search of classrooms, lockers, cars and the school grounds for a weapon. Authorities say there were no threats received.

“You’ll see the SWAT team is out here. The critical incident response team is also here, not because any weapon was seen or a threat was made, but simply because we need the additional manpower to search a campus of this size,” said Lt. Jeff Hallock of the Orange County sheriff’s department.

Parents remained on edge as officers conducted the campus-wide search.

“Especially after what happened in Santa Barbara, the kids should just go to school and be safe and not worry about this,” a visibly shaken parent said.

All staff members and students were ordered to shelter in place, according to KCAL9’s Michele Gile.

“Due to a suspicious object found on campus, students and staff are remaining sheltered in classrooms while law enforcement checks the area. All students and staff are currently safe and secure. We will continue to update you as information becomes available. Our phone lines are currently overwhelmed due to high volume. The principal’s emails and this website will be your best source of updated information,” the school’s website said.

Cellphone photos taken by a student show police making their way through the school. In the case of some kids, they say their teachers turned off all the lights and they hid under the desks.

“It is scary to them to see guard dogs and SWAT team members going up and down their school. And in light of recent incidents not knowing what could happen is very scary to them,” said a concerned parent.

Around 4 p.m., officials gave the school the all clear and students were allowed to leave the campus located at 3333 Golden Lantern Street in Dana Point.

Authorities said no weapons were found after a class-by-class search. No arrests were made.