An 18-year-old Texas high school student, injured when a snorkeling tour boat began sinking near Cancun, died on Tuesday, authorities in Texas reported.

The Dallas County Medical Examiner's Office confirmed the death of Lisa Chung, 18. She had been flown to Dallas on an air ambulance along with her parents earlier Tuesday.

Jason Chute, a spokesman for U.S. tour operator GradCity, identified the victim as Lisa Chung, although Mexican authorities have given her name as Lissa. U.S. embassy officials in Mexico City said they could not confirm the name.

Chung suffered heart and lung failure Saturday when the "Sea Star" catamaran began sinking between Cancun and Isla Mujeres. She was declared brain dead and was being kept alive by a respirator, officials said.

A preliminary report by the Cancun port captain said the boat is authorized to carry 80 people but may have been loaded with as many as 126 at the time it sank.

"Sea Star" Captain Agustin Cituk said the boat has a capacity of 250 people.

Chute also said the vessel was designed to carry 250, and described it as a 73-foot catamaran built less than six months ago. "It was nowhere near capacity," he said.

He said the snorkeling excursion was part of a package trip organized by GradCity, which has sent nearly 500 high school students and 32 chaperones to Cancun so far this summer.

"We're trying to find out what caused the boat to go under and the series of events following the boat partially sinking," Chute said.

Mexican officials are also investigating.