TORONTO (AP) — The union representing workers at Canadian National Railway Co. has taken down picket lines and said its workers will begin returning to work Friday.

However, the Teamsters said the work stoppage at Canada’s other major freight railroad, Canadian Pacific Kansas City Ltd., remains ongoing, pending an order from the Canada Industrial Relations Board.

The Canadian government forced the country’s two major railroads into arbitration with their labor union late Thursday afternoon, a move aimed at averting potentially dire economic consequences across the country and in the U.S. if the trains are sidelined for a long period.

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The government’s action came more than 16 hours after Canadian National and CPKC locked out workers over a labor agreement impasse. Both railroads said they would work to get trains moving again as soon as possible.

The unprecedented work stoppage led Canada’s labor minister to refer the dispute to the Canada Industrial Relations Board to impose binding arbitration. The union and Canadian Pacific Kansas City Ltd. officials met with the board Thursday and will meet again Friday.

CPKC said it was prepared to discuss the resumption of service at the meeting with the CIRB, but the union refused and wants to make submissions to challenge the constitutionality of Labour Minister Steven MacKinnon’s direction.

The union representing 10,000 engineers, conductors and dispatchers at Canadian National and CPKC Canada responded angrily to the order Thursday, accusing the railroads of intentionally creating a crisis to force the government to intervene.

The government ordered the railroads into arbitration with the Teamsters Canada Rail Conference to end the lockout that began at 12:01 a.m. Thursday after the two sides were unable to resolve the contract dispute.

All of Canada’s freight handled by rail - worth more than $1 billion Canadian (US$730 million) a day and adding up to more than 375 million tons of freight last year - stopped Thursday along with rail shipments crossing the U.S. border. About 30,000 commuters in Canada were also affected because their trains use CPKC’s lines. CPKC and CN’s trains continued operating in the U.S. and Mexico during the lockout.

Many companies in both countries and across all industries rely on railroads to deliver their raw materials and finished products, so they were concerned about a crisis without regular rail service. Billions of dollars of goods move between Canada and the U.S. via rail each month, according to the U.S. Department of Transportation.