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LITTLETON, Colo. (KDVR) – Fire investigators found there was a gas leak at a Littleton home, which caught fire Sunday after an explosion and sent six people to the hospital.

South Metro Fire Rescue said investigators were finishing up at the scene on South Broadway around 3:15 p.m. Sunday.

“They are unable to confirm the exact ignition source, but they have confirmed there was a gas leak in the home prior to the explosion and fire,” South Metro said in a tweet.

Six people were transported to the hospital. Their condition was listed as stable.

Firefighters located the fire in the basement of the home and were ventilating the structure on Sunday afternoon.

People inside the home reported an explosion before the fire started, knocking out windows. South Metro safety officers were using thermal imaging cameras to continue monitoring heat and smoke coming from the basement.

Traffic was delayed in the area of South Broadway and Orchard Road. Southbound Broadway was closed near the fire scene. Smoke from the structure was visible in the area.

FOX31 reached out to Xcel Energy for an update on their investigation. The company released this statement:

“Our thoughts are with the people affected by this incident. We are working with fire officials and emergency responders on the scene, and our emergency responders have completed safety checks of the area to confirm it is safe. We are coordinating with fire officials and after several performance checks, our systems are working as designed. Protecting the safety of the public and our employees is a core value and we take it very seriously.”