The distress call that halted a clean-up of a massive oil spill Wednesday in northern Alberta turned out to be a false alarm.

The call for help came over the workers' radio system around 9:30 a.m.

"We initiated our man down procedure," said Stephen Bart, spokesman for the pipeline owner Plains Midstream Canada.

The company sounded an alarm and had workers congregate at muster points for a head count, he said. The site was evacuated and the company did a search by ground and air. 

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Plains Midstream spokesman Stephen Bart details the company's man down procedure. (CBC)

Bart said all of the workers were accounted for. The clean-up is expected to resume Thursday morning.

About 4.5 million litres of crude oil spilled from the pipeline near Peace River almost two weeks ago.

Plains Midstream says more than a third of the oil spilled has been sucked up by vacuum trucks and skimmers.

About 300 employees are working 17-hour days.

The pipeline leak has been fixed, but the Energy Resources Conservation Board wants to ensure the risk of another break is low before allowing the oil to flow again.