A congressional committee is investigating Amazon over concerns that the tech giant may be endangering employees by making them work in unsafe conditions during tornadoes and other extreme weather events, says a letter sent this week to company CEO Andy Jassy by the committee.

The inquiry will examine the deaths of six workers last year who were killed when a tornado struck an Amazon warehouse near St. Louis, says the letter from the House Committee on Oversight and Reform. As the tornado approached, the letter says, supervisors at the facility reportedly threatened workers and contractors that if they left, they'd be fired or face other consequences.

The investigation will also take a broader view of Amazon's policies.

The situation regarding the tornado "was not an isolated incident," the committee says in its letter. "Amazon workers were reportedly required to stay on the job during deadly wildfires in California in 2018, extreme heat in the Pacific Northwest in Summer 2021, and dangerous flooding during Hurricanes Irma in 2017 and Ida in 2021."

The letter asks Amazon to provide the committee with documents related to the tornado event and to the company's policies around extreme weather situations, including emergency practices and disciplinary and termination policies. The committee wants the documents by April 14.

Amazon didn't immediately respond to CNET's request for comment. A company spokeswoman provided the following statement to The New York Times: "Our focus continues to be on supporting our employees and partners, the families who lost loved ones, the surrounding community and all those affected by the tornadoes. We will respond to this letter in due course." Last year, the company told Bloomberg that federal guidance and proper safety procedures had been followed at the warehouse during the tornado event.

Amazon's labor practices have been subject to increased scrutiny, with the company facing allegations of, among other things, insufficient precautions around COVID-19, illegal employee terminations, improper activity around unionization efforts, and inadequate bathroom breaks for workers.