A U.S. border officer shot the driver of a vehicle trying to cross into Mexico at a port of entry Thursday night, authorities said.

The unnamed officer attempted to stop the vehicle at the port in Nogales, Arizona, before allowing it to exit the country. But the southbound vehicle sped off, prompting the officer to fire his weapon, according to a press release from the U.S. Customs and Border Protection.

The vehicle subsequently stopped several yards across the border in Mexico. The driver sustained a gunshot wound and was taken to a local hospital in Nogales. The officer was not injured, according to the release.

The incident is under investigation.

A spokesperson for the U.S. Customs and Border Protection told ABC News on Friday that additional information is not immediately available.

Authorities temporarily shuttered the outbound lanes of the port of entry Thursday night.

Nogales Mayor Arturo Garino told the Arizona Daily Star that the driver refused to stop and attempted to run over the officer. Garino said he was told that the officer fatally shot the driver.

The mayor's office did not immediately respond to ABC News' request for comment.