Authorities have expanded the search area for a man missing since his bateau sank Monday in Bayou Manchac after they found his boat downstream in the Amite River, but the man remained missing at the conclusion of the third day of searching, state officials said Wednesday.

Crews found the boat at 4 p.m. Wednesday about 5 miles downstream from where the boat either sank or capsized Monday night, said Adam Einck, spokesman for the state Department of Wildlife and Fisheries.

“So it floated three miles downstream in Bayou Manchac and then another two miles downstream in the Amite,” Einck said in an email.

State officials have acknowledged that with so much time passed, the chances of finding Allen Fitzgerald, 23, of Prairieville, alive have greatly diminished.

Searchers still hold out hope of finding him alive, but the work became more a recovery effort early Wednesday.

“But more than anything, we’re just doing our best to find him,” Einck said.

High water and strong currents due to the heavy rains that fell earlier this week, and in earlier weeks, have made the search more difficult, Einck said.

Agents with the DWF Enforcement Division, the Ascension, Livingston and East Baton Rouge parish sheriff’s offices, and the St. Amant and Galvez fire departments had been searching a 4-mile stretch of the bayou, stopping near its confluence with the Amite before the search area was expanded Wednesday.

Authorities had brought in a helicopter Tuesday and continued Wednesday to use sonar and to drag the bayou’s bottom for signs of Fitzgerald and his boat.

Further details on the location of his bateau were not immediately available Wednesday night.

Fitzgerald’s family and friends declined a request for comment midday Wednesday as they waited for news in the parking lot of Big John’s Galveztown Landing and Storage off La. 42. Authorities have been putting out their search boats from the launch point along the bayou.

Fitzgerald and another man had been traveling in the 12-foot bateau on the bayou in Ascension Parish about three to four miles upstream of the Amite River on Monday night when the boat began taking on water, state wildlife officials said.

Fitzgerald’s passenger, who was in the front of the boat, jumped into the bayou before the bateau sank, but Fitzgerald remained in the back of the boat.

Einck said the surviving passenger and Fitzgerald had gone out about 3:30 p.m. Monday during a break in the severe rains earlier that day. They went down the bayou and onto the Amite River but had to stop under the La. 42 bridge over the Amite because the rains picked back up.

Einck said authorities do not know why the boat began taking on water.

But he pointed out that when it did take on water, the two men were on their way back up Bayou Manchac about 9 p.m. Monday in the face of strong currents in a small boat with a 6-horsepower engine.

The passenger who escaped made it to shore and found a house where he called 911 for help.

Authorities began searching at 10 p.m. Monday but stopped about five hours later, waiting for daybreak Tuesday.

Einck said the search continued all day Tuesday and Wednesday.

The passenger with Fitzgerald told wildlife officials that neither man was wearing a personal flotation device when the boat went down.

Einck said the bayou is not deep in the area being searched and authorities are hopeful that as water levels continue to drop, the chances of finding Fitzgerald will improve.

Follow David J. Mitchell on Twitter, @NewsieDave.