SAN FRANCISC0 (Reuters) - A man drowned on his 21st birthday after attempting to swim across a pond in northern California while carrying a 10-pound (4.5 kg) rock, the Los Angeles Times reported on Wednesday.

The California Highway Patrol told the newspaper that Austin Harr was with friends at a pond in the Oroville Wildlife Area on Monday evening when he slipped under the water.

After a few minutes passed, his friends grew worried and tried looking for him before calling for help, the newspaper said.

Rescue workers found him about an hour later, and he was pronounced dead at a local hospital, the Times said. Officials told the newspaper they believed alcohol played a role in his death.

(Reporting by Curtis Skinner in San Francisco; Editing by Tom Heneghan)