Police said Monday they are investigating whether a Cancun tourist boat was overloaded when it sank over the weekend, leaving a Texas woman brain dead.

Lissa Thang Chung, 18, of Dallas nearly drowned Saturday when the catamaran sank between Cancun and Isla Mujeres, said Luis Felipe Ortiz, police chief for the state of Quintana Roo.

She was declared brain dead after suffering heart and lung failure and was being kept alive by a respirator, Ortiz said.

A preliminary report by the port captain said the boat appeared to be carrying 126 people, though it was authorized to carry 80. The boat operator offers snorkeling trips.

Sea Star Captain Agustin Cituk insisted the boat has a capacity for 250 people and was not overloaded.