The cause of the Menemsha fire that destroyed the Coast Guard boathouse last July is undetermined, a report released by the U.S. Coast Guard this week concluded.

Investigators outlined three possible sources of the fire — a lit cigarette, faulty wiring under the Coast Guard boathouse or faulty wiring under the Chilmark public pier — but said none could be pinpointed precisely.

“Whatever it was, it was likely one of these three sources but we can’t say one over another,” said Capt. Verne Gifford, southeast sector commander for the Coast Guard in a public appearance at Station Menemsha on Wednesday afternoon. “We just wanted a fair process where all the investigative agencies were involved, where everyone had the opportunity to address it and everyone was dealt with fairly. I didn’t have an inclination or a desire for it to go one way or another, I just wanted an open and transparent process that was fair,” Captain Gifford said.

Released on Wednesday afternoon, the Coast Guard report rules out arson or any other criminal activity in connection with the fire. It also concludes that the fire did not start in the Coast Guard boathouse but at the connection between the two docks. “The deepest charring of the fire scene was in the area of the southwest corner of the boardwalk/pier,” the report says.

The seven-month investigation is now closed. The agencies involved included the Coast Guard Investigative Service, the state fire marshal, federal Bureau of Alcohol, Tobacco, Firearms and Explosives and the Chilmark police and fire departments. The report was first discussed at Station Menemsha on Wednesday afternoon in a meeting that was closed to the press and public, but included the Chilmark selectmen, police, fire and other town officials. The complete report is posted on the Coast Guard First District Web site at uscgnewnegland.com.

The fire occurred in the early afternoon on July 12, 2010, a steamy summer day at the height of the summer season on the Vineyard. Menemsha village was crowded with tourists, summer residents, fishermen and recreational boaters.

The Coast Guard report includes a large number of interviews that were conducted later with people who were in the village when the fire broke out. The names are blacked out.

One interview is with the Coast Guardsman who was in the boathouse using the exercise room when the fire first broke out and was one of the first to call 911.

“I was working out for about 20 minutes when I smelled smoke. I went out to the back of the weight room through the door. I turned the corner and moved about five to 10 feet when I saw the smoke . . . When I opened the door I noticed the arc of fire on the pier about 10 feet from the front of the door,” the Coast Guardsman said in the interview.

Collectively the interviews serve to recreate the scene that day in Menemsha. Winds were strong and out of the south-southwest, one fisherman recalled. An Island resident who was taking scenic photographs of the West Basin from Aquinnah when the fire broke out later provided fire investigators with the pictures captured in his camera. Digital time stamps were noted. An artist who was painting on Creek Hill was later interviewed. A charter captain documented the problems he had with the electricity on the dock.

All of Menemsha was evacuated and every firefighter on the Island responded to the scene. Firefighters battled the blaze well into the evening and were still on the scene the following morning. Miraculously there were no injuries save an Aquinnah firefighter who was injured in an accident during cleanup after the fire had been put out.

The historic 68-year-old boathouse, a landmark building with its red roof, was completely destroyed, along with the surrounding pier.

Following the closed-door meeting on Wednesday, Chilmark selectmen reacted to the report.

“It’s what we expected. We were a little disturbed it took this long and didn’t get an answer. Politically that’s to no one’s benefit,” said selectman Frank Fenner, Jr. “I was a little disturbed personally about them listing the town of Chilmark as a possible source because I went by it shortly after the fire started and there weren’t any flames on the town dock. I just don’t understand how the town dock could be an initial source of the fire.”

Mr. Fenner said the selectmen are now concerned about two things — the rebuilding of the boathouse and insurance claims.

Captain Gifford said a line item has been placed in the proposed 2012 federal budget for $10 million to rebuild the boathouse. If it is approved, the boathouse will not be rebuilt until late 2013 or early 2014, Mr. Gifford said.

Mr. Fenner said he wants to make sure that when it is rebuilt, it fits the character of the Menemsha waterfront.

“It takes a demanding presence there and it’s really a big part of what the harbor looks like so we want to make sure we have some input into its design into a new building,” he said. “We want something that’s in keeping with the neighborhood and doesn’t stand out like a sore thumb.”

The insurance claims process is another concern.

“I have my doubts whether there will be any monies in there for anybody,” Mr. Fenner said, adding:

“Regardless of the initial source of fire, the burning of the Coast Guard building caught these boats on fire . . . you would think there would be some responsibility. These are just local fishing guys and they don’t have any insurance on anything.”

He concluded: “We’ll try and put in a claim. This is a big bite to us. It’s $1.7 million plus, it’s at least that [to rebuild the pier].

“That’s something that we didn’t ask for, but I sympathize with the Coast Guard, they didn’t ask for that either.”