Det. Shawn McRae said, "They were pressurizing it to remove the fuel that was left in it and when it was pressurized the seam gave way and struck an individual."
J. Jesus Vidales Rivera, 51, of Tulare died from what appeared to be blunt force trauma.
Investigators believe the victim died on impact and are calling the incident a horrific accident.
The victim's wife and other family members were devastated as they showed up to the farm to retrieve some of his belongings.
Fire investigators say several men were working along with the victim. Unlike a propane tank, which is designed to sustain high pressure, the tank they were working on was a diesel fuel tank.
Mike Virden said, "It doesn't take a lot of pressure so if you just have slight pressure that the tank wasn't designed for you will have failure of the tank and that's what occurred."
Det. McRae said, "The individual was down trying to remove the last of the fuel when the tank gave way and he was directly in front of it."
Rivera worked at Nichols Farms just outside of Hanford. The owner, Chuck Nichols, told Action News that their thoughts and prayers go out to Rivera's family. He said they are cooperating fully with law enforcement and state inspectors, who will be checking the equipment to determine if any of the machines malfunctioned.