A house fire and explosion that killed a family of four in Ohio has been ruled arson, authorities said.
The state fire marshal's office said Wednesday that investigators have determined what caused the fire in Northfield Center Township, but they aren't releasing details while the investigation is underway.
According to Dominion East Ohio Gas, testing confirmed there was no natural gas leak from its lines at the home, about 15 miles southeast of Cleveland.
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Jeffrey and Cynthia Mather, both 43, were killed, along with their 8- and 12-year-old daughters, according to authorities.
Officials with the school district sent a letter to parents and guardians Tuesday identifying one of the daughters killed as a second-grade student at Northfield Elementary School.
"We are all deeply saddened by this loss and our deepest sympathies go out to those friends, relatives, and classmates they left behind," the superintendent wrote. "It breaks my heart to share this news."
Neighbors said the explosion Monday night shook homes throughout their development.
The fire marshal's office is working on the investigation with the Summit County sheriff's office and a local fire department.