In a significant embarrassment for American scientists, a U.S. research vessel conducting controversial sound-wave research off Mexico's Gulf coast faces heavy fines for running aground on a coral reef.

Mexican authorities announced on Thursday that the U.S. National Science Foundation ship Maurice Ewing (search) hit a reef about 30 miles off the Yucatan peninsula on Monday, even though the reef was clearly marked on maps.

Mexico's Attorney General for Environmental Protection, Jose Luis Luege (search), said the ship could be seized temporarily to ensure the fine is paid.

The ship is using sound waves to search for traces of an asteroid that may have wiped out the dinosaurs 65 million years ago.

"The fines will be based on the amount of damage done," said Mexico's Attorney General for Environmental Protection, Jose Luis Luege. "I can't say offhand what the fine will be, but it will be sizable."

The research project had already raised the hackles of environmental activists, who say the technology could harm sea life, including whales, which use sound waves to communicate.

The Monday accident, which authorities did not confirm until Thursday, fueled activists' opposition to the Maurice Ewing.

"They said they had state-of-the-art technology and highly trained personnel, but they couldn't even detect a sand bank or a coral reef?" said Rosario Sosa, president of the Yucatan-based civilian Association for the Rights of Animals and their Habitat.

The environmental protection agency called the accident "inexplicable," noting the reef was clearly marked on navigational charts for the area.

Officials with Columbia University's Lamont-Doherty Earth Observatory, which operates the Maurice Ewing, had no immediate comment on the accident.

The Mexican government said the accident affected about 20 square yards of underwater rock formations and about 10 square yards of coral.

"It takes coral a hundred years to grow one meter, so ten meters, that's like a thousand years lost," Sosa said.

Mexico's national Environment Department had already taken criticism for granting permits for the Maurice Ewing to operate in Mexican waters.

The scientists are using the underwater seismic pulses to learn more about the Chicxulub Crater, a depression measuring about 120 miles in diameter and centered outside the port of Progreso, 190 miles west of Cancun.

Straddling the shoreline, the Chicxulub crater is believed to have been carved by a comet or asteroid 65 million years ago. It occurred at the same time of a mass extinction of species including the dinosaur.