A man is in hospital with "major trauma" injuries after an industrial accident with a forklift truck, paramedics said.
The accident happened at Chestnut Building Centres on Picton Road, Wavertree, Liverpool, at 11:05 GMT.
The man, in his 60s, was taken to Aintree Hospital by air ambulance, where his condition remains critical.
Officers are working to establish the full circumstances of the incident, Merseyside Police said.
The site has been cordoned off while detectives speak to witnesses.