LONDON, Ont. -- Seven people were injured and about 100 homes had to be evacuated after a house explosion in a southwestern Ontario city caused a massive fire late Wednesday night.

The blast in London, Ont., was caused by a vehicle slamming into a home and hitting a gas line just before 11 p.m., police said. The ensuing fire then spread to several residences overnight, with crews still on scene Thursday morning, authorities said.

Acting Deputy Fire Chief Jack Burt said the blast had completely destroyed the home that was hit by the vehicle, noting that the residence was empty at the time.

“There's a hole in the ground,” he said. “This was a significant explosion.”

Four firefighters, two police officers and one civilian were taken to hospital, authorities said. One firefighter was in serious condition while the others had minor injuries and were released, they said.

Police said a 23-year-old woman, Daniella Alexandra Leis, was charged with impaired driving in connection with the incident.

About 100 residences in the neighbourhood had to be evacuated, a city spokeswoman said, with seven of those homes “severely impacted” by the fire. The blaze was largely put out by Thursday afternoon, authorities said.

Brian Magee, who lives a few doors down from where the blast occurred, was among several residents who gathered near the scene on Thursday. He said he had gone outside with his son just before 11 p.m. the night before after seeing first responders in the area.

“All of a sudden 'boom' - that's when the gas line blew,” he said, adding that the force of the blast caused the windows of his home and other nearby residences to shatter.

Magee said he rushed to shield his son from the debris that was scattered across the neighbourhood.

“I just grabbed my son and put him down like a little turtle so it could hit me,” he said, adding that he and his family had to leave their home as the fire spread.

“I'm upset. My kids are upset,” he said, adding that the family cat has gone missing.

Keara-Lynn Douglas, who also lives in the neighbourhood, said she felt her house shake when the blast occurred. She said she went outside and saw an orange glow a few blocks away, which prompted her to drive to the scene.

“There was just debris everywhere,” she said. “It was insane.”

Local councillor Jesse Helmer, who is also an area resident, said he initially thought a tree fell on his house.

“I went outside and saw a huge plume of smoke and fire going up into the sky,” he said.

A community centre was opened for displaced residents and other residents have dropped off food and water, he said.

“It's important that we get together as a community,” said Helmer. “Everyone is really coming together to put up some donations and things that people will need because some of these people have lost everything.”

Fire Chief Lori Hamer said her crews would be assessing structural damage to the homes to determine when residents could return. The city said some of those displaced by the incident have been put up in hotels.

-- with files from Alanna Rizza in Toronto.