MARQUETTE - The Marquette City Fire Department was dispatched this morning to a natural gas explosion in a home on South Lake Street.
Fire officials said just after 8 a.m. they were called to the 1000 block of South Lake Street after a passerby called 911 to report that they smelled natural gas from the street.
The fire department arrived to find the front and south side windows of the home had been blown out by a natural gas explosion and lay in the yard.
Natural gas requires an gas-air mixture of between 5 and 15 percent to ignite, according to Fire Chief Tom Belt. If the ratio is below 5 percent, Belt said, the mix is too lean to ignite. More than 15 percent, and it's too rich.
Belt said that they've determined that the explosion came from the home's hot water heater.
"The hot water tank ignited just a small portion (of gas) which was within the flammability range ... and that caused a small explosion that traveled through the duct-work," he said.
The explosion caused moderate structural damage to the basement and first floor, but Belt said the explosion was actually kept at bay by the extremely rich concentration of natural gas throughout the rest of the house.
He said the situation was "very unusual" - only the second time in 40 years he's seen it.
Upon arrival, firefighters shut off the gas supply to the house and ventilated the area. They then entered and searched the home, determining that it was unoccupied.
Belt said the homeowners are from Bloomington, Ind. and have not lived in the house this winter.
It is still unknown where the gas leak originated, and the incident remains under investigation by the fire department and SEMCO Gas. SEMCO will investigate the property on Sunday, according to Belt.
The Marquette Police Department and SEMCO assisted at the scene.