OAKLAND (CBS SF) — A marathon bargaining session between Bay Area Rapid Transit management and its two biggest labor unions that began Wednesday morning lasted all night and was continuing Thursday, BART spokeswoman Alicia Trost said.

Members of Service Employees International Union Local 1021 and Amalgamated Transit Union Local 1555 are still threatening to go on strike if an agreement isn’t reached on a new contract, but they have agreed to keep working and keep BART trains running while negotiations continue.

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Asked how long the negotiating session will last, Trost said, “There’s no schedule.” Management representatives, including BART General Manager Grace Crunican, and union leaders are still at the bargaining table, along with three federal mediators.

Trost said the mediators have imposed a gag order barring the parties from telling the news media and the public how the negotiations are going.

Negotiators also participated in lengthy bargaining sessions earlier this week. Talks that began on Monday didn’t end until 5:30 a.m. the following day, and talks that began on Tuesday afternoon last until about 1 a.m. Wednesday.

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The key issues in the contract talks are wages and employees’ contributions for their health care and retirement plans.

BART workers previously went on strike for four and a half days at the beginning of July, after their previous contract expired, but they have been at work since then as negotiations have continued.

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