It will take months to complete an investigation into the March 12 sinking of the tugboat Specialist and the deaths of its three crewmen at New York’s Tappan Zee bridge, Coast Guard officials said days after the vessel was raised from the Hudson River.

“This is a major marine casualty,” Lt. Cmdr. Eric Rivera, chief of investigations, Coast Guard Sector New York, said in a lengthy statement detailing steps ahead. “It is the total loss of a commercial vessel of more than 100 gross tons. In addition, we have loss of life, which adds a layer of complexity.”

The 84’x26’x9’ 2,400-hp Specialist, operated by New York Marine Towing Inc., was one of three tugs moving a tower crane barge downriver when its starboard side hit another barge anchored at the construction site of the new New York Thruway bridge. The tug sank quickly around 5:20 a.m.

Capt. Paul Amon, 62, of Bayville, N.J., and crewman Timothy Conklin, 29, of Westbury, N.Y., and Harry Hernandez, 56, of Staten Island, N.Y., all died. The body of Hernandez could not be recovered until March 24 when the Chesapeake 1000 heavy lift crane barge from Donjon Marine Co. Inc., raised the tug.

The construction area is on the north side of the Tappan Zee bridge, which has carried New York Thruway traffic over the river between Westchester and Rockland counties since the late 1950s, and is to be replaced by the $3.9 billion new bridge in 2018. Gov. Andrew Cuomo said radio traffic just before the allision indicated the crew realized they were too close to the construction barge and needed to move left.

Coast Guard officials said those communications are being examined in the investigation, which will also include digital recordings and photographs from the tug’s last trip and witnesses. In addition to crew on the two accompanying tugboats, 14 construction workers were on the barge when the Specialist hit.

The Coast Guard is getting help too from New York state agencies, the National Transportation Safety Board and the Westchester County Police Department.

“Westchester Police Department has played an important role in the Coast Guard investigation,” Rivera said, adding that the Coast Guard was relying on local police handling, compiling and storing physical evidence.