LITTLETON, Colo. (KDVR) — Witnesses described a scary situation after what was reported by occupants as an explosion at a home in Littleton.

“We were coming down Broadway and we saw, like, three fire trucks coming behind us,” Mark Williams said.

Williams, who saw the aftermath, said several South Metro Fire Rescue trucks sped past him Sunday morning while on Broadway near Orchard Road. They were headed to a home in Littleton.

“You see the smoke, there’s a lot of smoke at first, then we walked to see the whole front window was blown out. It was, like, terrifying,” Williams said.

When they got to the home, fire officials said smoke was billowing out of windows.

“They found a fire located in the basement,” Connor Christian, spokesperson for South Metro Fire, said.

Incident commanders upgraded the incident to a mass casualty event because of the number of people treated. In all, seven were hurt but are recovering.

Officials tell us children were also inside.

“I did speak to a person that was in the home and he felt the home actually move when he reported hearing this explosion,” Christian added.

“They also said they were smelling gas before that happened,” Christian said.

Fire officials said the people were staying here temporarily, and that the home is a short-term rental.

South Metro Fire worked with Xcel Energy to confirm a gas leak at the house, but they did not immediately find the source of ignition.

“They are checking all of the different meters that all around the home,” Christian said.

Williams said he saw the family shortly after the reported explosion.

“The family was out in the front yard, they had medics around them and everything,” Williams said. “They looked like they were OK, but still, it’s a horrible thing to happen on any day.”

South Metro Fire said the injuries were minor and all of those impacted were in stable condition.