Four fishermen were missing off the Texas Gulf Coast Saturday, more than a day after their boat sank about 115 miles southeast of Galveston, according to the U.S. Coast Guard.

The coast guard searched an area about the size of Delaware overnight. (Coast Guard News/Flickr).

Reuters reported that the Coast Guard received a distress signal from a 50-foot (15-meter) fishing boat at about 3:30 am CDT Friday.

The boat, based out of Galveston, began sinking about 115 miles southeast of Galveston, not far from the Texas-Louisiana border, reported the Associated Press.

A Coast Guard jet dispatched to the area. About five hours later, at 8:30 am, crew member John Robinson was spotted waving his arms aboard an orange raft.

Robsinson was rescued by helicopter and returned to Galveston Friday. He told the Coast Guard he was unsure of what had happened to the other four fishermen aboard the boat, according to Petty Officer Richard Brahm.

According to the Associated Press, the U.S. Coast Guard is using boats, a helicopter and airplanes in the continuing search. So far, rescuers have canvassed a 2,000-square-mile (3,200-square-km) area, but have not found any evidence of the missing fishermen.

"We're going to keep searching until someone tells us to stop," Brahm said

He noted that the Coast Guard uses a variety of factors to determine whether there is a possibility the men could still be alive, according to the Associated Press.