Washington, Dec 14 (IANS): The Occupational Safety and Health Administration (OSHA) in the US has opened an investigation into the collapse of an Amazon warehouse in Illinoi that left six people dead.

The roof had collapsed after a powerful tornado hit the Amazon warehouse on December 10.

"OSHA investigates all workplace fatalities and we are supporting them," Amazon spokesperson Kelly Nantel told The Verge late on Monday.

The probe agency will have six months to complete its investigation and propose penalties if it determines safety or health regulations were violated.

In addition to the six people killed at the Amazon warehouse, 45 were rescued, according to media reports.

Former Amazon CEO Jeff Bezos had said in a tweet that his "thoughts and prayers" were with the families of the workers who died.

"All of Edwardsville should know that the Amazon team is committed to supporting them and will be by their side through this crisis," Bezos tweeted.

One of those who died, Clayton Cope, 29, spoke to his family on the phone shortly before the building in the town of Edwardsville was struck, according to a BBC report.

Questions were being raised over whether adequate shelter was available, whether workers were advised to go there immediately, and whether the shifts should have gone ahead that evening at all, given the warnings of severe weather, the report said.

Amazon said that the team worked "incredibly quickly" to ensure as many employees and partners could reach the "shelter in place" site.

One cargo driver, Austin J McEwen, 26, died in the bathroom, where many workers said they had been directed to shelter after receiving emergency alerts on their mobile phones.