Port Authority police found the abandoned vehicle midspan of the bridge's westbound upper level around 9 p.m. Sunday.
Among the agencies that sent air and sea units to assist were the NYPD, Palisades Interstate Parkway Police, the Nyack and Piermont fire department marine units, the Thiells dive team, the Irvington and Tarrytown fire departments, the Rockland County Sheriff's Office and the Westchester County Police Aviation Unit.
An investigation was continuing Monday, Port Authority police said.
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