What they thought was smoke filled the third floor at a Bessemer, Alabama warehouse on Friday, according to a report from the retail, wholesale and department store Union. Workers on the other floors were allegedly left to continue working as an unidentified vapor spread throughout the facility.

Workers on the third floor evacuated around 1:30pm. Hours later, workers started seeing the smoke-like substance and did n’t evacuate until 5:45pm. They were n’t notified from a fire alarm, managers, or through the go screens and a to Z app that Amazon uses to communicate with its workers.

The rwdsu says there was’limited’ police and fire presence in the building. Employees were reportedly told to go inside and begin working despite the’cloudiness’ inside the building.

I do n’t know what I was breathing in for that long, and I does n’t know if it’s still in the air at work today either,’ said Isaiah Thomas, an Amazon warehouse worker at the Bessemer location.

Workers have reported the situation to the occupational health and safety administration. The smoke was likely vaporized oil, but it remains unclear whether it poses any health risks.

An air conditioning malfunction resulted in smoke emitting from the equipment, says Amazon spokesperson Kelly nantel.’out of an abundance of caution, we evacuated the facility and called the local fire department who responded and quickly evaluated and cleared the site. We’re thankful no one was injured and we appreciate the swift actions of the Bessemer fire department’.

Nantel says the fire department’s investigation found no evidence of hazardous conditions. She also denies the rwdsu’s claim that employees were told to clock out and take vto upon evacuating.

The Verge reached out to the rwdsu with a request for comment but did n’t immediately hear back. The Verge did not immediately hear from the rwdsu.

Workers at Amazon’s Bessemer warehouse have long been fighting to unionize. Union organizers accused Amazon of meddling with the election. The National Labor Relations Board later determined that Amazon violated us labor laws.

The Amazon warehouse collapse happened in edwardsville, Illinois, on March 27. Update update update: updated to add context surrounding the collapse.

Kelly nantel’s statement to the verge was updated March 8:04pm. The statement was updated on March 27.