Over 900 schools in the Los Angeles Unified School District were closed on Tuesday morning after “an unspecified threat was received,” however schools within the Santa Clarita Valley remain unaffected.

The decision was prompted by an “electronic threat” received early Tuesday and the threat “is still being analyzed,” said school district police Chief Steve Zipperman in an interview with CNN.

The “message” referred to backpacks and “other packages,” said District Superintendent Ramon Cortines to CNN. He added that many schools were threatened, though none by name. The threat was toward students in schools.

No threat has been received at any school in the Santa Clarita Valley, said Shirley Miller, public information officer for the Santa Clarita Valley Sheriff’s Station.

However, as a preventative measure, deputies will be conducting patrol checks at all area schools throughout the day on Tuesday, she said.

The LAUSD Board President Steve Zimmer confirmed that all students are safe within the district.

“We’ve got all resources to secure and make sure all of the campuses are safe, as well as the bus lots and checking all of the buses,” said L.A. City Councilman Mitch Englander. “Under the abundance of caution, there’s no reason to put any kids or families or people at risk.”

Englander added that, while no city blocks are being closed in a particular area, “we want folks to understand and be flexible with their families and their employees. This is certainly the first time we’ve seen this happen.”

However, students that have arrived at a school with the LAUSD will be with staff until parents or guardians can be contacted, according to a tweet by the LAUSD. The school district is requiring parents or guardians to bring a valid ID when picking up their child.

“There are faculty at all of the schools that have been identified, they do have contingency plans in place at all of the schools for any kind of situation like this,” said Englander. “The best thing to do is check with your local school as well as certainly to go by the school.”

Englander spoke with L.A. Mayor Eric Garcetti, who is in talks with the Metropolitan Transportation Authority about allowing students to ride buses at no cost on Tuesday, he said.

The Los Angeles Unified School District, or LAUSD, is the second largest district in the nation and enrolls more than 640,000 students at over 900 schools, according to the district’s website.