NEW YORK (AP) – The city’s crippling three-day mass transit strike ended Thursday after union leaders — facing mounting fines, possible jail terms and the wrath of millions of commuters — voted to return their 33,000 members to work without a new contract.

Union board members who emerged from the organization’s headquarters said workers will return to their job sites starting with the next shifts. The vote was overwhelmingly in favor of returning to work, and resuming negotiations with the Metropolitan Transportation Authority.

“We thank our riders for their patience and forbearance,” said Transport Workers Union President Roger Toussaint.

It was unclear when the city’s buses and subways would again start running, although transit officials said it would take 10 to 18 hours to restore full subway service. Union employees working the evening shifts were expected to report as soon as possible.

“It can’t be turned on and off with a flip of a switch,” Mayor Michael Bloomberg said of the mass transit system. But he said buses should be running by Thursday evening, with most subways operating for the Friday morning rush hour.

The announcement of the vote came outside union headquarters about 3 1/2 hours after state mediators said a possible deal was worked out.

Toussaint, the combative president of Transport Workers Union Local 100, had recommended that his union’s executive board accept the deal. But the vote was immediately blasted by dissidents who felt the union had caved in.

“This was a disgrace,” said TWU vice president John Mooney. “No details were provided to the executive board. (Toussaint) wants us to discuss the details after Christmas.”

The proposed deal would put the nation’s largest mass transit system back in operation while negotiations on a new three-year deal resume between the union and transit authority. But it does not resolve the contract dispute, raising the specter of another walkout if negotiations were to fail.

“I think it was all for nothing,” said commuter Lauren Caramico, 22, of Brooklyn, about the strike. “Now the poor people of the TWU are out six days pay, and nothing gained.”

Both sides returned to a midtown Manhattan hotel for serious discussions at about 1 a.m. Thursday and met through the night.

“This was a positive day,” said mediator Martin Scheinman. “It was a very positive night. We wouldn’t be here otherwise.”

The walkout, which began at 3 a.m. Tuesday, was the first citywide transit strike in 25 years; the workers left their jobs in violation of a state law prohibiting them from striking.

The walkout sent millions of commuters from the city and its suburbs scrambling to find alternate ways of getting to work, and inflicted a heavy toll on the city’s economy in the week before Christmas.

Before the deal was announced, an off-duty firefighter was critically injured Thursday when he was struck by a private bus while riding his bike to work. It was the first serious strike-related injury.

The upbeat mood at the announcement of the tentative deal was in stark contrast with the bitter rhetoric of the last two days, when Bloomberg traded barbs with Toussaint. Gov. George Pataki, another strident critic of the union, hailed the possible deal as “very positive for all New Yorkers.”

Both Pataki and Bloomberg had urged the MTA to avoid further negotiations until the union was back on the job. Bloomberg, at a City Hall news conference, praised New Yorkers for their handling of the strike.

“We passed the test with flying colors,” he said. “We did what we had to do to keep the city running, and running safely.”

Striker Ralph Torres, a Manhattan bus driver, said word of a possible deal spread quickly though the rank and file. A return to work, in addition to restoring his paycheck, would halt the imposed fines for every union member of two days pay for every day on strike.

“I’m ready to work the rush hour this afternoon if they let me,” he said from the picket line on West 41st Street.

The breakthrough was announced just minutes before Toussaint and two of his top deputies were due in a Brooklyn courtroom to answer a criminal contempt charge for continuing the strike in defiance of a court order.

A day earlier, State Supreme Court Justice Theodore Jones said he would consider fining, or potentially jailing union leaders Thursday if transit workers remained off the job.

He has already fined the union $1 million per day while the strike lasts, although that penalty has been frozen while the TWU appeals.

The tentative deal came without the MTA pulling its pension proposal, which Toussaint had said one day earlier was a sticking point. Curreri said the MTA “has informed us it has not withdrawn its pension proposals but nevertheless is willing to discuss whether adequate savings can be found in the area of health costs.”

The union opposed a proposal raising contributions to the pension plan for new workers from 2 percent to 6 percent. Curreri said there would be a news blackout during further negotiations, as agreed to by both sides.