On Tuesday, another call led to lockdowns at Northview Intermediate School and adjacent Duarte High
School, both located on the same campus. Again on Thursday, the Arcadia Police Department put Arcadia High on lockdown after the receiving a similar gun threat.
All of the calls turned out to be hoaxes.
Ari Dekofsky, an FBI spokeswoman confirmed that the FBI is working with local law enforcement agencies on the investigation.
"The FBI is part of a coordinated effort among the affected juriscictions and their police departments to find the person or persons responsible for the hoax calls," she said. "We are providing assistance as requested with various resources."