Amazon chief Jeff Bezos on Saturday said that he was “heartbroken” after learning that at least six people were killed at an Amazon warehouse in the US state of Illinois when it was struck by a tornado.

In a post, Bezoz said, “The news from Edwardsville is tragic,” as the town where the facility was located when it was struck by a tornado.

“We’re heartbroken over the loss of our teammates there, and our thoughts and prayers are with their families and loved ones,” Bezoz said.

Also read: Monstrous tornado hits Kentucky hard as storms leave dozens dead in 5 states

The warehouse was struck by a series of tornadoes that ripped across six US states, killing more than 80 people in total in what President Joe Biden said was likely to be “one of the largest” storm outbreaks in history.

Up to 100 Amazon employees working a night shift ahead of Christmas are believed to have been trapped when the warehouse collapsed, and it is not clear how many may still be trapped.

On Saturday, Edwardsville fire chief James Whiteford told reporters that 45 people made it out of the building safely, one had to be airlifted to hospital for treatment, and at least six had died.

Also read: In storm’s aftermath, Kentucky residents struggle with loss

But he said the operation had turned from rescue to focus “only on recovery,” fueling fears the toll could yet rise.

“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.

Also read: Biden will do ‘whatever needed’ to help states affected by tornadoes

“We extend our fullest gratitude to all the incredible first responders who have worked so tirelessly at the site.”

A monstrous tornado, carving a track that could rival the longest on record, ripped across the middle of the U.S. in a stormfront that killed dozens and tore apart a candle factory, crushed a nursing home, derailed a train and smashed an Amazon warehouse.

Also read: Kentucky faces ‘most devastating tornado’ in history

In Kentucky alone, 22 were confirmed dead by Saturday afternoon, including 11 in and around Bowling Green. But Beshear said upwards of 70 may have been killed when a twister touched down for more than 200 miles (320 kilometers) in his state and that the number of deaths could eventually exceed 100 across 10 or more counties.