Image copyright Getty Images Image caption All workers were displaced after the massive pile of brick and cement collapsed
The Occupational Safety and Health Administration has opened an investigation into a large pile of bricks that collapsed at a US Amazon warehouse, killing one worker and injuring nine others.
The brick and cement mix fell on a group of 20 people on Tuesday evening in Chester, Illinois.
One of the injured people was reported to be in a critical condition.
It is the second fatal incident at an Amazon warehouse this year.
Two workers died in June after a cardboard box fell on them as they were stacking items on shelves.
Image copyright Getty Images Image caption An Amazon spokesperson said all workers were safe and secure at all times
The spokesman for the union that represents Amazon warehouse workers, Mark Snyder, said the company had had warnings about structural integrity of the pile.
In September, Amazon said it was “reviewing how we can better protect the safety of our employees” after a man suffered a neck injury when bricks toppled over at its Virginia warehouse.
The company did not immediately respond to requests for comment on Friday about the Chester incident.
It is the second big workplace tragedy at a US Amazon warehouse this year. Two workers died in June when a cardboard box fell on them as they were stacking items on shelves.
Separately, two employees were killed after a forklift fell at a company warehouse in Tennessee in December.
In both of those incidents, there were plenty of warning signs that a wall of cardboard could cause risk.
The size of the shipment the brick and cement had been used to stack was also not perfectly suited for the building, safety experts have told the BBC.
The Amazon spokesperson said the roof of the Chester building, which is in Chester, Illinois, was inspected by inspectors on Tuesday.
“We are actively cooperating with OSHA to understand all of the details and to investigate the incident,” he said.
“We have two shipping centres in Chester with thousands of associates working hard to support our customers,” he added.
Amazon said all workers were safe and secure at all times.
Image copyright Getty Images Image caption Ten people were injured in the incident
It also said an investigation into whether any firm was at fault or whether the incident was caused by any factor like wind or clouds had been launched.
In his statement, Mr Snyder, president of the United Food and Commercial Workers Union Local 15, said the union was working to get federal investigators on site to determine the reasons for the collapse.
“We are appalled that in the wake of the tragic injuries and deaths resulting from Amazon warehouse operations, that OSHA has chosen to conduct a cursory inspection of this facility,” he said.
“No one is above the law and no one is exempt,” he added.
Workplace safety experts said they were concerned a similar tragedy could happen again.
There is a significant amount of material to handle that is not suitable for the warehouse, said Mary Kay Mallonee, who heads up analysis company Decision Toolkit’s projects for the US.
“That wall would not stand up,” Ms Mallonee told the BBC.
“Even if workers started to stack on top of that, it would have collapsed by then.”
A spokesman for the Department of Labor, the agency which leads OSHA investigations, said the agency would check with the Illinois Department of Labor to see if the Occupational Safety and Health Administration had any issues with the factory’s safety practices.