BATH – The search for a man presumed dead after a construction crane fell into the Kennebec River is expected to intensify Thursday when crews try to salvage the crane.

The crane operator, 48-year-old Steven Oldham of Felton, Del., has been missing since the crane fell from a barge last Thursday afternoon near Bath Iron Works. Another worker, William Larkins, 43, of Epping, N.H., was rescued.

The men had been dredging the river to make way for a floating dry dock.

Local and federal officials continue to investigate the accident.

A salvage crew from Weeks Marine Inc. of Cranford, N.J., is expected to begin lifting the 250-ton crane from about 70 feet of water sometime Thursday, according to Louise Pulizzi, a spokeswoman for Clark Construction of Bethesda, Md. Weeks Marine owns the crane.

Clark Builders of Maine is the project’s general contractor, but several subcontractors – including Atkinson Construction and its subcontractor, Weeks Marine – are assigned work at the job site. Oldham and Larkins are Weeks Marine employees, Pulizzi said.

The cause of the accident remains unclear. Bath police and the U.S. Occupational Safety and Health Administration are conducting separate investigations.

“Frankly, there is not a lot to go on at this point. I am hopeful that once we bring up the crane, it will shed more light on what happened,” said Bath police Chief Peter Lizanecz.

Bill Coffin, OSHA’s district supervisor in Portland, said he probably won’t know the cause of the accident until late January.

Brunswick police had sent an airboat to the shoreline on both sides of the river at low tide, but did not find Oldham’s body.

The Maine Marine Patrol did not conduct any search Sunday, Monday or Tuesday, but planned to resume efforts when the salvage operation begins.

Floating chunks of ice, freezing temperatures and murky water caused by the dredging have made it too dangerous for divers to return.

David Mercier, who is coordinating the effort for the Maine Marine Patrol, said the body may have become attached to the crane. Mercier said he met with workers Tuesday to tell them he is not sure that Oldham’s body will ever be found.

“I just don’t know,” he said. “For closure sake, I hope we do.”