BOSTON (AP) – Many of the 1,900 NStar workers who walked off their jobs Monday say their strike has more to do with worker and public safety than with money – a contention the electric and gas utility calls a diversion from more important financial issues.

Safety questions about NStar’s electrical service in eastern and central Massachusetts were a public issue even before the walkout began after the sides failed to agree on a new labor contract to replace one that expired at 12:01 a.m. Monday.

State regulators last month hired an engineering consultant to review safety issues raised by incidents in which at least three dogs were fatally shocked by so-called “stray voltage” from underground NStar lines in recent years, said Paul Afonso, chairman of the state Department of Telecommunications and Energy. Another consultant is reviewing recent underground explosions that have dislodged manhole covers, in one case injuring a man.

“We’re hopeful the consultants can dig into the root causes so we can better understand these incidents,” Afonso said.

Boston Mayor Thomas Menino recently named a joint city-NStar task force to address the stray voltage issue, and NStar’s chief executive, Thomas J. May, promised to locate and fix such sites.

Mike Murphy and Mike Walsh, underground electrical inspectors who were among a group of 10 NStar workers picketing Monday outside NStar’s headquarters in Boston’s Back Bay section, both said the No. 1 strike issue is safety for workers and the public. They said NStar is not committed to hiring enough staff to conduct preventive maintenance.

“They want until things blow up and then fix them, and that’s how they do maintenance,” said Walsh, a 22-year employee who took part in a monthlong walkout in 1986, the last strike against NStar or its predecessor companies, Boston Edison Co. and Commonwealth Electric.

The Boston-based investor-owned utility has accused the Utility Workers Union of America’s Local 369 of discussing safety with the media but not at the bargaining table.

Timothy Manning, an NStar human resources vice president, said in a prepared statement that the union was “rebuffing our offer to add 132 union jobs, dedicate specific crews to maintenance work, and enhance safety and training programs.”

The offer to add more jobs comes after NStar required workers completing repair jobs to also conduct maintenance while at repair sites. Previously, NStar had limited maintenance to crews assigned specifically for upkeep rather than repairs.

No talks are scheduled in the dispute, which involves issues including company-proposed cuts to dental and vision coverage for retirees, forced overtime, and a proposed two-tier pension system that would cut benefits for new workers.

NStar said it also is seeking to eliminate a rule requiring it to pay overtime to workers who make repairs to overhead power lines during late afternoon. Those workers’ shifts typically end in the mid-afternoon, “despite the fact that statistically most power outages occur during the afternoon,” the company said in a news release.

NStar said its linemen earned an average of $97,000 last year “in addition to receiving world-class health care benefits, access to the company pension plan, and a 40(k) plan with a company match.”

Murphy and Walsh, of the union, both said they don’t consider the company’s proposed pay hikes to be a sticking point. The men said they make around $90,000 a year, with about one-third of that total coming from overtime that often amounts to more than 20 hours a week.

NStar said it expects service to about 1.1 million electric customers and 300,000 natural gas customers will continue “running smoothly and safely” despite the walkout. The company, with nearly two-thirds of its 3,000 employees on strike, is assigning managers and contractors to oversee energy distribution.

The union represents linemen and engineers across NStar’s service area in the Boston metropolitan area, Worcester and coastal areas from Cape Cod to Cape Ann.

The sides reported no system disruptions Monday and no problems between picketers at seven locations and NStar workers who remained on the job.

Afonso, of the Department of Telecommunications and Energy, said the state agency was devoting more staff to monitoring NStar’s service performance because of the walkout.

NStar shares rose 72 cents to close at $57.02 in Monday trading on the New York Stock Exchange.