The explosion and fire blazed through the Southfork Dairy Farms near the town of Dimmitt in the southern US state of Texas, on Monday night.
"This was the deadliest barn fire for cattle in Texas history and the investigation and cleanup may take some time," said Sid Miller, Texas Agriculture Commissioner.
Overheated equipment is likely to have caused the fire, according to the Castro county sheriff Sal Rivera.
He said methane may have "ignited and then spread out with the explosion and the fire," and that fire marshals need to investigate further to confirm.
Police and firefighters rescued one person that was trapped inside, a female agricultural worker who is now being treated at a hospital in Lubbock in northwestern Texas.
It was not immediately possible to contact the owners of the farm, according to officials.
A video posted on Twitter showed footage of the barn, which is said to be more than 2.1 million square feet (approximately 198,000 square meters).
The fire prompted the Animal Welfare Institute, one of the oldest animal welfare charities in the US, to urge Texas to impose federal regulations protecting animals.
"Farms must do more to protect animals by adopting commonsense fire safety measures," tweeted the institute.
