SAN DIEGO — Two men hiding in the trunk of a U.S. citizen’s car died on Tuesday, apparently as they tried to enter the United States through southern California, the San Diego Fire-Rescue Department said.

The 2012 Dodge Challenger entered the San Ysidro Port of Entry in the afternoon and was sent to a secondary inspection, where officials using scanning equipment uncovered the men, U.S. Customs and Border Protection spokeswoman Angelica De Cima said.

A 28-year-old man and a 20-year-old man were found unconscious and not breathing in the car, which was driven by a 41-year-old U.S. citizen, De Cima said. The driver was arrested. Customs agents alerted police and tried to revive the men.

De Cima said the investigation into the alleged “illegal entry attempt” was ongoing.

One of the men died at the scene and the other died at an area hospital, a fire official said.

De Cima said the cause of death was not known and the investigation was still ongoing into the alleged “illegal entry attempt.”