Law enforcement vehicles were deployed to Walnut High School and Mt. San Antonio College in Walnut, California, after news of a bomb threat. Pictured: Los Angeles Police Department Officers deploy around Santa Monica College after multiple shootings were reported there in 2013. GETTY IMAGES

A bomb threat in Walnut, California, led to the lockdown of Walnut High School and an evacuation at Mt. San Antonio College Thursday. The threatened time for explosions at the Los Angeles-area schools was 2:45 p.m. PDT (5:45 EDT), said school officials.

"Calmly leave campus. Classes/services are closed until at least 4:30pm. NOT A DRILL," the school's official account tweeted.

Los Angeles County law enforcement responded to both scenes, which are about 3 miles from each other, according to news station KABC. Mt. San Antonio College is the largest community college in the United States with 52,954 students. Located south of the community college, Walnut High School is attended by 2,669 students. The two schools are in eastern Los Angeles County.

Students at Walnut High took to Twitter to raise concerns about the school's decision to lock the building, as opposed to evacuate along with Mt. San Antonio College.

Mt. San Antonio College classes will be closed until 4:30 p.m. PDT, school officials said.

Photos were posted to social media of students evacuating the campus. The school's campus security blocked the entrances.

This story is developing and will be updated as information becomes available.