CHICAGO, (Reuters) – The U.S. Occupational Safety and Health Administration has opened an investigation into the Friday night building collapse at Amazon.com Inc (NASDAQ) in Illinois. A U.S. Department of Labor official said Monday.

OSHA has six months to complete its investigation, issue citations and propose monetary penalties if violations of workplace safety and or health regulations are found, Scott Allen, a U.S. Department of Labor regional director for public affairs, said via email. According to him, compliance officers are present at the site from Saturday.

Police said six workers died when an Amazon warehouse in Edwardsville (Illinois) buckled under the power of the storm. The destruction of homes and businesses along with the death toll left by six tornadoes in the U.S., which raged through six states, left more than 200 mile (322 km) of damage.

Amazon did not respond immediately to our request for comment.

According to the National Weather Service, the tornado occurred between 8:28 p.m. on Friday and 8:32 pm local time. The storm intensified as it struck Amazon Warehouse. Peak winds at 150 miles an hour (231, kph) were recorded. The storm was strong enough to rip off the roof and cause concrete walls that measured 11 inches (28cm) in thickness, which was more than a football field.

Amazon workers made it safely to safety. The authorities gave up on the hope of finding survivors and shifted to rescue and recovery efforts expected to last just days.

Three facilities are located in Edwardsville by the company: the damaged delivery station, a fulfillment center and an order sorting station. In July 2020, the delivery station was inaugurated to receive orders and deliver them to their customers last mile.