(Reuters) - The U.S. Coast Guard late on Thursday suspended its search for four Americans who were aboard a small airplane that is believed to have gone down in the Bermuda Triangle near the Bahamas.

The plane, a Mitsubishi Corp MU-2B twin-engine turboprop, was reported lost on Monday after failing to arrive at Titusville, Florida, 40 miles (64 km) east of Orlando on Florida’s Atlantic coast. It had departed Borinquen, Puerto Rico, at about 11 a.m. local time that day.

The plane’s four occupants, Jennifer Blumin, 40, Nathan Ulrich, 52, and Blumin’s 3-year-old and 4-year-old sons are still missing, the Coast Guard said in a statement late on Thursday.

“This was a swift and significant loss and its impact has reverberated through everyone that participated in the search,” Christopher Eddy, search and rescue mission coordinator, said in a Coast Guard news release.

The U.S. National Transportation Safety Board is investigating the cause of the accident.

A Coast Guard helicopter crew found a fuel sheen and a debris field on Tuesday in ocean waters near the Bahamas.

Blumin, a resident of New York City, is the founder and chief executive of Skylight Group, a firm that leases large buildings as event venues for fashion shows and celebrations, according to the New York Times.

Ulrich, who is from Lee, New Hampshire, co-founded a scooter company called Xootr more than a decade ago.

The Bermuda Triangle -- covering an area roughly between Bermuda, Puerto Rico and the tip of Florida -- is known in popular culture for the unexplained disappearance of ships and aircraft.