TORONTO (AP) — The Canadian mediator tasked with resolving a complicated railroad labor dispute to protect the North American economy has ordered workers at the country’s two largest railroad companies to return to their jobs so both can resume operations.

Saturday’s order means Canadian National can continue train service, which it resumed Friday morning, just over a day after workers were locked out. But the CPKC railroad likely won’t be able to resume service until 12:01 a.m. Monday, when workers were ordered to return.

The Teamsters union, which represents the workers, said it would comply with the Canada Industrial Relations Board’s order and send its members back to work, but would also take legal action against the arbitration award.

“This decision by the CIRB sets a dangerous precedent. It sends a message to the Canadian economy that large companies only have to shut down operations for a few hours and cause short-term economic losses, and the federal government will step in and break up a union,” said Paul Boucher, president of the Teamsters Canada Rail Conference, which represents more than 9,000 train drivers, conductors and dispatchers at both railroads.

“The rights of Canadian workers are significantly limited today,” Boucher added.

Labor Minister Steven MacKinnon ordered an end to the lockout just 16 hours after it began because government officials could not bear to watch the economic disaster if the railways remained closed.

MacKinnon acknowledged the board’s decision in a post on social media platform X, saying he expected the railroad and its employees to resume operations as soon as possible.

Businesses across Canada and the United States said they would quickly find themselves in a crisis without rail service, as they rely on freight railroads to deliver their raw materials and finished products. Without regular deliveries, many companies may have to limit production or even close.

Canadian National trains were running again on Friday morning, but the union threatened to strike there starting Monday morning. Saturday’s order nullifies that strike threat. CPKC workers have been on strike since the lockout began early Thursday, and the railroad’s trains are at a standstill.

“While CN is disappointed that an agreement could not be reached at the negotiating table, the company is pleased that this order effectively ends the unpredictability that has negatively impacted supply chains for months,” the railroad company said in a statement. “CN remains focused on safely returning the movement of goods as efficiently as possible.”

CPKC officially ended its lockout following Saturday’s decision and ordered workers to return to the day shift on Sunday. However, union spokesman Christopher Monette said the striking workers will not return to CPKC until Monday, the deadline set out in the order.

CPKC said it wanted to “get the Canadian economy back on track as quickly as possible and avoid further disruptions to supply chains.”

The previous contract, which expired at the end of last year, will remain in force for the duration of the arbitration process. The board has instructed the unions not to further disrupt operations during the process.

While Canadian railroads struggle to reach agreements with their union, major U.S. railroads have reached a series of deals in recent days.

CSX announced the first contracts on Wednesday – months before the current contract expires and before the start of the traditional national bargaining process that typically drags on for years – and announced seven more contracts on Friday. In total, the new contracts cover more than half of the railroad’s workforce. Norfolk Southern and BNSF followed suit, each announcing four contracts with some of their 13 unions on Friday.

The agreements will help the U.S. railroad industry avoid difficult labor disputes of the kind that pushed it to the brink of a strike two years ago before Congress and President Joe Biden intervened to push through a collective bargaining agreement.