Police say they were investigating a Long Beach taxi driver on an unrelated matter when they discovered thousands of child pornography images and videos on his phone.

Thomas Stanford, 38, was arrested Monday and charged with five counts of child porn possession.

Long Beach police say they obtained a search warrant for Stanford's phone but wouldn't say what the initial investigation was about.

There was no comment from Beech Street Taxi, for which police say Stanford worked for the last three years.

Police say Stanford's hack license, which is required to drive a taxi, has been revoked. He was being held on $500,000 bail.