One woman died and 36 people were detained after as many as 70 people tried to swim around a fence that juts into the Pacific Ocean at the border of the United States and Mexico, the authorities said on Saturday.

The group attempted to swim from Tijuana into Border Field State Park in San Diego late Friday evening, the Border Patrol’s parent agency, Customs and Border Protection, said in a statement.

Border Patrol agents called paramedics after discovering an unresponsive woman who was believed to have been part of the group of swimmers. Agents and emergency medical responders provided aid, but the woman was declared dead around 12:30 a.m., according to the statement.

Agents took 36 Mexican nationals into custody, including 25 men and 11 women. They were brought to a nearby Border Patrol station.

Some of those detained had been pulled from the ocean. The Coast Guard, which dispatched two cutters and a search helicopter, took 13 people from the water and handed them over to the Border Patrol, said Adam Stanton, a Coast Guard spokesman.