US regulators have opened an investigation into the collapse of an Amazon warehouse in Illinois after it was struck by a tornado on Friday, leaving six people dead and another in hospital.
Occupational Health and Safety Administration inspectors, who have been at the site in Edwardsville since Saturday, will look into whether workplace safety rules were followed and will have six months to complete the investigation, said spokesperson Scott Allen.
Amazon said workers at the warehouse had little time to prepare when the National Weather Service declared a tornado warning on Friday night.
The tornado arrived soon after, collapsing both sides of the warehouse and caving in its roof.
Amazon spokesperson Kelly Nantel said the warehouse received tornado warnings between 8.06pm and 8.16pm on Friday, and site leaders directed workers to immediately take shelter. At 8.27pm, the tornado struck the building.
Mr Felton said most of the 46 people in the warehouse known as a “delivery station” headed to a shelter on the north side, which ended up “nearly undamaged,” and a smaller group to the harder-hit south end.
The company said those are not separate safe rooms but generally places away from windows considered safer than other parts of the plant.
The investigation in Illinois came as workers, volunteers and members of the National Guard were spreading across tornado-damaged areas of Kentucky to assist with recovery tasks ranging from replacing thousands of damaged utility poles to delivering bottles of drinking water.
In Kentucky, Governor Andy Beshear said the death toll could grow as authorities continued to work around debris that slowed recovery efforts.
Nearly 450 National Guard members have been mobilised in the state.
“With this amount of damage and rubble, it may be a week or even more before we have a final count on the number of lost lives,” the governor said.
Kentucky authorities said the level of destruction was hindering their ability to tally the damage.
As searches continued for those still missing, efforts also turned to repairing the power grid, sheltering those whose homes were destroyed and delivering supplies.
Across the state, about 26,000 homes and businesses were without electricity, according to poweroutage.us, including nearly all of those in Mayfield.
State and local officials said it could take years for some of the hardest-hit areas to fully recover.
“This again is not going to be a week or a month operation, folks. This will go on for years to come. This is a massive event,” Mr Dossett said.
Five twisters hit Kentucky in all, including one with an extraordinarily long path of about 200 miles , authorities said.