SAN DIEGO -- Mexican authorities Thursday fired shots that pierced the windshield of a van carrying 40 people moments before the vehicle crossed into the United States in San Ysidro and ended up in Otay Mesa, authorities said.

U.S. border authorities called San Diego police for backup at 4:40 a.m. after the van was stopped on northbound Interstate 905 at Picador Avenue, according to San Diego police Sgt. Ray Battrick. There are conflicting reports about whether the van was driven the wrong way on I-905.

Several people fled on foot up a hillside, 10News' Rachel Bianco reported on 10News This Morning Thursday. A man and woman inside the van were wounded. Authorities said that the woman was shot in the foot and the man had a graze wound to a leg.

Two people were taken to UCSD Medical Center, a San Diego Fire-Rescue dispatcher said.

U.S. Customs and Border Protection is handling the investigation.

No other details were immediately available.