Two men have died in upstate New York after falling into a manure tanker, local police said.

One of the men attempted to retrieve a piece of equipment that had fallen into the tanker, the Kirkland Police Department told WKTV.

“He passed out and fell inside of the tanker,” police said, adding that the second man also passed out and fell in as he tried to help.

The incident happened on Thursday morning at a farm in Kirkland, New York, less than 50 miles (80km) east of Syracuse, New York.

Decomposing manure can produce a number of gases, including methane, ammonia and carbon dioxide, that can be deadly to people and livestock when ingested in high concentrations, according to the Farm Safety Association.

Authorities identified the men as Nathan Doody, 33, and Tyler Memory, 29, according to the New York Daily News.

Workers on Champion Farm called authorities to help, but the men were taken to hospital, where they were pronounced dead.

Similar incidents have happened previously. A farmer and 13 cows died in Wisconsin in 2016 after they were overcome by methane or sulphur oxide from a huge manure holding tank.

An Iowa father and son died after being overcome by the fumes in a hog manure pit.