(CNN) -- Ferry service between San Francisco and points north will be suspended Tuesday morning in anticipation of an expected protest, a regional transportation agency said. The Golden Gate Bridge, Highway and Transportation District announced Monday that there will be no ferry service across San Francisco Bay between the northern California city and Larkspur and Sausalito until about 2 p.m. Tuesday. The agency said it has been engaged in ongoing contract talks with unions representing 375 of its employees, with the next negotiating meeting set for May 7. It said there were reports there will be anything from informational picketing on the Golden Gate Bridge to efforts to shut down traffic on the bridge as well as all ferry services, though those possibilities have not been confirmed by the unions themselves.
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NEW: Other unions' members plan to support ferry workers, among other May Day activities
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A Bay Area transit agency says ferries won't run from Marin County early Tuesday
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It's due to fears that an expected union action will negatively affect service
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The union is urging members to participate in a "rally" on the Golden Gate Bridge
These include "supporting striking ferryboat workers at @placeholder ferry terminals" between 7 and 10:30 a.m.