MERCER CO., Ohio (WDTN) – Authorities in Ohio say three brothers have died after they became stuck in a manure pit and were overcome by fumes.

The deceased were as brothers Gary, Todd and Brad Wuebker. Rescue crews found them unconscious on their family’s farm.

The village’s fire chief says the brothers were fixing a manure pump before they passed out from the fumes. All three were taken to area hospitals and later pronounced dead.

A preliminary autopsy of two of the brothers showed they died by asphyxiation secondary to a farm accident.

Manure pits are common on large livestock farms, but they can produce dangerous gases including hydrogen sulfide and carbon monoxide.

It’s not clear how the men got stuck in the pit or how long they were in there.

The Associated Press contributed to this report.