STOCKTON, Calif. - A plea for help from from a girl who held up a sign while in a car travelling on a Northern California highway turned out to be a hoax, authorities said.

The California Highway Patrol said six patrol units responded Saturday to a highway near Stockton after callers reported seeing a girl in the back seat of car holding a sign that read “Help me shes not my mom!! Help!!”

The message was first spotted when the car was travelling on southbound Highway 99 near Elk Grove. Officers caught up with the vehicle about 20 miles (32 kilometres) later near Stockton and made “a high-risk stop,” the CHP said.

The CHP said the driver pulled over immediately and officers talked to the girl’s mother.

“The mother was unaware of what her daughter was doing,” it said

Officials said the mother and daughter were allowed to leave the scene.

“This is a reminder that parents need to be aware of what their children are doing in the back seat at all times,” the CHP said in a social media post.