TECATE, Calif. -- Two men are facing smuggling charges after Border Patrol agents discovered 16 Mexican nationals inside a cargo trailer of a semi-truck early Thursday morning in Tecate.

According to a Border Patrol news release, agents spotted a group of suspected illegal immigrants at about 3 a.m. near the Tecate Port of Entry.

The group was observed as they walked to a nearby semi-trailer rig parked in a parking lot, the news release stated.

After watching as people boarded the trailer, and seeing the driver of the semi-truck lock the trailer doors with a heavy-duty padlock, agents moved in.

The agents found 13 men and 3 women inside the trailer. All were arrested, along with the 41-year-old male driver of the semi-truck, officials said.

A 26-year-old Mexican national, who was among the group inside the trailer, is also suspected of helping to smuggle the illegal immigrants across the border, according to the Border Patrol.

He and the driver are being charged with alien smuggling by Immigration and Customs Enforcement (ICE), agents said.