A home in Austin, Texas, was leveled and at least 23 others were damaged on Sunday in an explosion of unknown causes that could be heard for miles and left six people injured, the authorities said.
The explosion happened just after 11 a.m. local time in a northwest section of Austin, according to the Austin Fire Department.
The cause of the explosion was under investigation. The authorities said there was no signs of criminal activity in connection with the explosion.
“We believe this is certainly an isolated incident,” said Division Chief Wayne Parrish of the Austin Fire Department. He said there was no gas service to the residence but it did have propane tanks.
A two-story house where the explosion happened collapsed and a neighboring home partially collapsed, the authorities said.
Two occupants of the home where the explosion occurred were taken to a hospital. One of them was in critical condition and the other was in serious condition, Capt. Shannon Koesterer of the Austin-Travis County Emergency Medical Services Department told reporters at a news conference.
An occupant in a neighboring home that was damaged was in critical condition, Captain Koesterer said. Another person had minor injuries, and two firefighters also had minor injuries, the captain added.
The authorities said they had accounted for all of the people who were in the affected residences at the time of the blast.
Officials said that garage doors and windows nearby were blown out and a car at the residence where the explosion happened caught fire. Power was out in the surrounding area because of damage from the explosion, the authorities said.
The blast could be heard as far away as Georgetown, Texas, which is about 30 miles north, Chief Parrish said.
The Police Department in Cedar Park, which is about 20 miles away, said on social media that it was aware of the “loud boom that was heard and felt throughout the city.”
Several agencies responded to the scene, including Austin-Travis County E.M.S., the Austin Police Department, the Travis County Sheriff’s Office and the F.B.I., Chief Parrish said. The Travis County fire marshal will lead the investigation, he said.