Los Angeles police investigating who was behind dry ice explosion in LAX bathroom

Los Angeles police have taken over the investigation into who was responsible for planting a plastic bottle containing dry ice that exploded in an employee bathroom at Los Angeles International Airport.

Air traffic was back to normal Monday after the Sunday evening explosion caused a commotion in LAX's terminal 2. Up to four flights were delayed after airport police halted security screening for more than an hour.

Los Angeles Police spokeswoman Sally Madera said no injuries were reported, and "there was no threat to the public area."

The bathroom was in an area of the terminal that isn't accessible to the public, according to FBI spokeswoman Laura Eimiller. She said there was "no stated threat associated with the incident."

Investigators are trying to determine how the bottle wound up there.