Police have named two men who are being treated in hospital after falling into an offal pit at a Staffordshire meat processing plant.
Glynn Thompson from Weston Coyney and Ivan Torr from Kingsley Holt were overcome by fumes at the plant.
Firefighters using a crane took 90 minutes to rescue the workers at John Poynton and Sons in Cheddleton, near Leek, on Sunday afternoon.
The men were airlifted to University Hospital of North Staffordshire.
Inquiry started
Mr Torr is said to be in a stable condition, while Mr Thompson remains in a critical condition.
Some paramedics and firefighters were also treated because of the fumes.
A Health and Safety Executive spokeswoman said: "The inquiry is at a very early stage but our understanding is that one of them may have gone in to clear a blockage and got into difficulty and his colleague went in to help."
Mr Thompson and Mr Torr, who are both believed to be in their 40s, were revived by paramedics before being taken to hospital.
Neil Bacus, from Staffordshire Fire and Rescue Service, said: "It was difficult to get lines down to them and make them fully secure before pulling them out.
"The important thing was to get oxygen to them in the first instance. That kept them going until we got to them."