Lockdown lifted at Alhambra High School after anonymous threat

Alhambra High School was briefly placed on lockdown Tuesday afternoon as authorities investigated an anonymous threat.

The school was placed on lockdown around 3 p.m., but no details on the threat were given. 

During the lockdown, the district tweeted about "concerns regarding a photo that was airdropped to some students." Though the district didn't offer any explanation, it said police confirmed that the photo was not a matter for concern.

Just over an hour after the lockdown began, the district tweeted that the lockdown had been lifted, and that the school would resume "regular afterschool activities."

"We thank APD for their diligence and the students and families for their patience during the investigation," the district wrote in its tweet.

About seven miles away, the Arcadia Police Department is conducted an investigation at Arcadia High School, but quickly determined there was no threat.

Earlier Tuesday, El Camino Real High School in Woodland Hills was placed on lockdown after a reported gunman on campus. The threat was deemed not credible by the Los Angeles Police Department and the lockdown has since been lifted.