UNION MILLS | A motor malfunctioned and ignited grain dust, causing a fatal explosion Monday at a Co-Op in Union Mills, officials said.
The ruling Wednesday came a day after a fire erupted in the silo where the blast occurred, triggering an evacuation of nearby homes.
Lisa Rosebaum, of the 800 block of Second Street, said the evacuation Tuesday evening was voluntary so she, her husband and two sons chose to stay.
"We wanted to wait and see what was going to be happening with it," Rosebaum said.
The black smoke billowing from the facility was heavy at times, she said.
"The smoke would get worse, then better and flame up again," Rosebaum said.
LaPorte County Police Chief Deputy Jim Sosinski said investigators looking for the cause of Monday's blast opened up the silo from the top to drop a thermal imaging scope inside.
When exposed to oxygen in the air, the smoldering grain began to "flame up," Sosinski said.
The black smoke was caused by a rubber belt on a conveyor that moves the grain, he said. Officers went door to door with a voluntary evacuation in case there was another explosion.
Tuesday night's storm helped douse the flames. The fire was still out when investigators went back inside the silo Wednesday and found scorching on two motors that operate a conveyor system at the grain elevator, he said.
One of the motors was in the silo's basement, while the other motor was higher up on a decking.
Investigators could not determine if both or just one of the motors was the ignition source, Sosinski said.
"It appears those motors were overheating and very possibly had been the source of ignition for the grain dust," he said.
James Swank, 67, of Union Mills, was working on a platform more than 100 feet up the concrete silo when the impact from the explosion caused him to fall to his death.
Nearby residents said the blast shook their houses.
Sosinski said the voluntary evacuation Tuesday lasted about two hours.
Although Rosebaum's family stayed, the group was ready to act if the situation worsened.
"We got our stuff ready to go just in case," Rosebaum said.