It happened just before 11 p.m. at a home on Grumm Road in Hardyston, Sussex County, rattling nearby residents.
No one was home at the time, and no injuries were reported.
While the cause of the explosion remains under investigation, the Sussex County Prosecutor's Office is said to be looking into two 100-pound above-ground propane tanks that were on the property. Authorities said one was about 30 percent full of fuel and the other about 20 percent full before the explosion.
"There was a spark, either from the ignition of the furnace or the hot water heater or something like that," the fire marshal said.
Residents in neighboring towns reported hearing the blast and called 911, with some initially believing it to be an earthquake.
Caller: "I think the house next door to me blew up."
Dispatcher: "Yeah, everybody, every-, is it on fire? Do you see a fire anywhere?"
Caller: "Yes, there's a fire."
There are conflicting reports whether the homeowner was away on vacation or had moved out recently.
"It sounded like lightning striking a house, and then the ground just shook," one neighbor said. "My entire car rumbled."
The home was across the street from Wallkill Valley Regional High School, and debris may have cracked windows and caused other minor structural damage at the school.
The school was closed Wednesday and Thursday, but was expected to reopen on Friday with a 2-hour delay to give staff time to clean up.
The 8th-grade and freshman dance has also been canceled.
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