San Francisco police are investigating a report that a teen girl was possibly sexually assaulted, robbed, and kidnapped and then left in Berkeley early Wednesday, police said.

A resident called 911 at 5:06 a.m. after the girl was heard yelling for help in the 2900 block of Piedmont Avenue at Ashby Avenue, said Berkeley police spokeswoman Officer Jennifer Coats.

The girl told police that the attack began in Oakland, Coats said. Oakland police got the report at 6:21 a.m., a department spokeswoman confirmed.

It was later discovered the incident originated in San Francisco and that agency is investigating, a San Francisco police spokesman confirmed late Wednesday.

The girl, whose age and identity were not released, was transported to an East Bay hospital, but her condition was not released. Police said the case may be linked to human sex trafficking, but did not say if they believe the teen is a sex worker.

Oakland police spokeswoman Officer Johnna Watson said Oakland is not the lead agency on the case but will assist outside police investigators if needed.

Contact Kristin J. Bender at kbender@bayareanewsgroup.com. Follow her at Twitter.com/kjbender.