Three farmworkers died on Wednesday after falling into a manure silo in the northern Netherlands, with a survivor flown to hospital in a critical condition, police said.

“Three men died and a fourth has been taken to hospital in a critical condition,” police spokesman Paul Heidanus told AFP of the accident in the village of Makkinga.

Emergency services, including helicopters and rescue divers, scrambled to the farm after the men fell into the silo on Wednesday morning.

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All four men worked on the farm, police said.

The silo is around 10 metres (30 feet) high and was almost empty at the time, police said.

“There was practically no manure in the silo, just a few centimetres,” Heidanus said.

Local newspaper the Leeuwarder Courant said on its website that one of the men had gone into the silo to clean.

He was wearing a gas mask but felt unwell, and the other three men tried to help him, the newspaper said.

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Manure silos emit a number of potentially dangerous gases, including hydrogen sulfide which can cause asphyxiation or unconsciousness.

Hot weather can cause more of the dangerous gases to be produced, with Wednesday the hottest day of the year so far in the rural northern Netherlands.

Police said that rescue workers cut a hole in the side of the silo to get the casualties out.

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“The investigation must establish what happened. How did they get into the silo, whether it was because of a fall, if gas played a role, we don’t yet know,” Heidanus said.

Makkinga is surrounded by farmland around 35 miles (50 kilometres) southeast of provincial capital Leeuwarden.