Passengers were evacuated and departure flights halted Monday at a Los Angeles International Airport (search) terminal after a man slipped through security without being properly screened.

The Transportation Security Administration (search) ordered the precautions as airport police searched for the man, who had not passed properly through a security screening station in the terminal that houses American Airlines and Australia-based Qantas Airways.

"All we know is that this person was not properly screened, but we also know that he did not run away from the screening station," said Nancy Castles, a spokeswoman for the TSA.

The man may not have known police were looking for him, she said.

Airport officials obtained a photograph of the man from a surveillance camera but were not immediately able to find him, Castles said.