The U.S. Coast Guard suspended its search late Saturday for a crew member missing after a tugboat sank that morning in the Mississippi River near Convent in St. James Parish.

The crew member has not been identified.

The towboat Miss Natalie sank close to mile marker 163 near Convent at about 8 a.m. Saturday, according to a Coast Guard news release.

Dive and salvage operations for the boat began Sunday morning, according to the news release. The river was closed between mile markers 158 and 162 during Saturday’s search and was reopened Sunday morning.

“Based on several eye witness accounts … we have determined that the missing crew member was onboard the vessel when it sank,” Cmdr. Kelly Denning, of Coast Guard Sector New Orleans, said in the release.

The release said four of the five crew members were able to escape and were rescued by a good Samaritan. Ryan Tippets, a Coast Guard spokesman, said none of the four was injured.

It remains unclear what caused the tugboat to sink, but the Coast Guard is investigating, he said. Tippets said there were no reports of extreme river or weather conditions in that area Saturday morning, and none of the crew had reported any problems with the boat to the Coast Guard.

A Coast Guard helicopter crew, divers and a sonar team were deployed Saturday to assist in the search.