BART officials and union representatives are reportedly working with a federal mediator toward a settlement in an effort to end the strike that has halted the transit system’s operations since Friday, according to the San Francisco Chronicle.

No in-person meetings took place over the weekend, but sources from the unions and management say they had been in contact with a federal mediator during that time to discuss a possible end to the almost four day strike, according to the Chronicle.

Although the unions and BART management reached an agreement regarding economic issues such as wages, medical coverage and pensions, negotiations broke down after BART management sought to implement changes to work regulations.

On Sunday evening, SEIU 1021 and Amalgamated Transit Union Local 1555, two unions which represent a majority of BART employees, offered another proposal that allow for work rule changes with technology but retain work rules preventing unsafe conditions.

A BART board meeting that had been scheduled for Monday 3 p.m. to discuss labor negotiations was canceled.

However, a regular board meeting remains scheduled for Thursday 9 a.m. in Oakland. According to the BART Board of Directors agenda, a closed session to discuss labor negotiations will be held during the meeting.

If the strike is called off, it would still take BART employees about 16 hours for employees to restart the train system since they have to “report back to work, fire up dormant systems and run test trains” to ensure safety, according to the San Jose Mercury News.

Oakland Mayor Jean Quan said in a tweet that she has been “in contact with both sides” and is “hopeful trains can be running tomorrow.”