A catamaran carrying dozens of foreign tourists on a pleasure cruise capsized off Costa Rica on Thursday, killing four people, emergency officials said.

The boat, which was on a day trip to the popular Tortuga (Turtle) Island, sank completely about 9 miles off the country's central Pacific Coast.

Firefighters Corps director Hector Chavez said initial reports of an explosion and fire were mistaken. Survivors reported that strong waves filled the boat with water and caused it to sink, he said.

Private boats in the area took in passengers until rescuers arrived.

Tour operator Pura Vida Princess reported that the 100-foot catamaran left Marina Los Suenos in the morning with 98 passengers and a crew of 10.

Rescuers had recovered 94 people from the shipwreck and taken them to two emergency centers on land. Authorities were awaiting the arrival of one last rescue boat to make a complete accounting of those on board.

The dead were not immediately identified.

According to the Pura Vida Princess website, the Tortuga Island day trip costs $125 and includes meals, a DJ, snorkeling and open bar.