HARTFORD, Conn. — Electric Boat is laying off nearly 100 employees, company officials said Friday, citing factors including the Navy’s decision to cancel the repair of an attack sub that was severely damaged by an arsonist.

A union that represents workers at the Groton submarine builder said it was told by the company to expect as many as 500 layoffs over the next few months. A company spokesman, Robert Hamilton, declined to comment on projections for layoffs beyond the 94 employees who were recently given notices.

The Navy contractor had been expected to play a major role in the repair of the USS Miami, which was set on fire while it was docked at a Maine shipyard in May 2012. The cost of the repair job was estimated at about $450 million, but the Navy decided to scrap the Groton-based attack submarine because of budget cuts and concerns that repair costs would run higher.

Robert Nardone, an Electric Boat vice president for human resources, said the company’s workload is falling off because of cancellation for repairs on the USS Miami as well as the USS Springfield.

“The projected workload is not expected to sustain current employment for the foreseeable future,” he said.

Electric Boat has about 12,250 employees, with 9,250 of them in Connecticut. There was a spike in employment earlier this year at the shipyard, where jobs rise and fall with the demands of the Navy, and company officials said at a legislative briefing in January that a slowdown was expected later this year.

Ken DelaCruz, president of the Metal Trades Council at the Groton shipyard, said Electric Boat told the union to expect between 450 and 500 layoffs over the next four months.

He said most of the layoffs were already planned before the loss of the Miami was announced, but the repair could have kept 300 workers employed for a long period of time. Last year, the U.S. Navy awarded a $94 million contract to a team led by Electric Boat to prepare for the repair of the USS Miami at Portsmouth Naval Shipyard in Kittery, Maine.

DelaCruz said the shipyard workers have been hit hard by the loss of repair and construction work due to budget cuts.

“We’re hoping Congress comes up with funding here and ends this madness,” he said.

U.S. Rep. Joe Courtney, a Democrat, said he is working with Electric Boat and the Navy to find new opportunities for the company to help offset the lost work.

“The hardworking men and women of Electric Boat remain critical to the support and construction of our submarine force, and I will continue to do all I can to mitigate these reductions in the weeks ahead,” he said.

A shipyard worker, Casey James Fury, of Portsmouth, N.H., was sentenced to 17 years in prison after admitting he set fire to the Miami, which was undergoing a 20-month overhaul at the Kittery shipyard.

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