WASHINGTON — A Marine fired his weapon while on duty along the U.S.-Mexico border in California and reported afterward that he had been attacked inside his vehicle by three people, officials said Friday

John Cornelio, a spokesman for U.S. Northern Command, which oversees the military's mission on the border, said the matter is under investigation. He confirmed that the Marine discharged his weapon but said he could not provide details until the investigation is completed.

Cornelio said the Marine was at a mobile surveillance camera site near El Centro, California, in the pre-dawn hours of May 29 when the incident took place. Cornelio said there were no reported injuries.

The Marine's name was not released.

The Marine is among about 2,100 active duty troops assigned to support the Border Patrol along the southwest border. Among their major tasks is assisting Border Patrol with vehicle-mounted surveillance cameras.