The Port Authority says the surprise strike staged by thousands of longshoremen Friday is over, NBC New York reported.

The workers had walked off the job at Port Authority terminals in New York and New Jersey Friday afternoon, all but shutting down one of the nation's busiest port networks.

The Port Authority said in a tweet that full operations were being restored Friday evening, "thanks to the expedient efforts" of the unions involved. Gates will open as scheduled on Feb. 1.

Members of the International Longshoremen's Association, one of the primary rank-and-file unions at the ports in New York City and New Jersey, stopped working about 10 a.m., according to the Port Authority. The stoppage affected all of the terminals in the port system, which receives nearly 30 percent of all cargo on the East Coast.

A spokesman for the union said the walkout took many union officials by surprise. Another union official told NBC 4 New York the strike was spurred by a bevy of grievances including concerns about the Waterfront Commission of New York Harbor's role in collective bargaining, regulations on time off after injuries and drug testing protocols.