DENVER (CBS4)– Nine people were injured, one critically, on Tuesday afternoon when a large explosion rocked a Denver neighborhood. The blast, which is believed to have been caused by natural gas, heavily damaged a four-plex residential building located on Santa Fe Drive between 3rd and 4th Avenue.

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It also damaged cars on the street and caused damage to a building across the street.

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“As you can see, the devastation behind us is pretty significant,” said Denver Fire Capt. Greg Pixley.

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One person was trapped and had to be rescued by emergency crews and two of those who were injured were rushed to the hospital. One of those patients suffered traumatic, severe injuries.

Denver Fire spent Tuesday night on scene combing the rubble with cadaver dogs. While there is no indication someone is missing, responders want to make absolutely sure.

One man found himself in the middle of the chaos. Alex Ponton was driving past the row of homes on 368 North Santa Fe when the explosion occurred.

“It threw it (the car). Like it was like ‘boom’ and it flew and then all the rubble started pushing into me…” Ponton said. “Next thing I know I’m stumbling out of my car. I can’t see anything there’s dust there’s people screaming.”

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Instead of running away, the young man ran toward the screams.

“I heard somebody screaming, just followed the voices, tore some stuff apart and there they were,” he said.

“We don’t know if all the victims were inside or outside. We know there were people inside,” said Pixley.

Gabriel Cruz works with Ponton at the nearby auto dealer, Rickenbaugh. He was also driving nearby when the explosion occurred.

“I thought something literally just rear-ended me it was that powerful,” said Cruz.

Cruz pulled over to see what was going on, that’s when he saw Alex and other co-workers run toward the rubble.

“I just remember seeing three coworkers just run toward that way and I was calling their names like ‘Don’t go that way! Don’t go that way.’”

Cruz said he barely had time to think, and he’s proud his coworkers were there to help.

“Until we can remove some of the debris, we’ll have greater clues about the cause. Natural gas lines come from either the street or the alley,” said Pixley.

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Pixley also confirmed that fire crews also extinguished a fire when they arrived on scene.

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Copter4 flew over the scene where the entire middle section of the building had been blown apart with pieces of lumber and bricks scattered into the street.

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A vehicle was in the middle of Santa Fe Drive, covered in dust.

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Witnesses say two explosions with shockwaves happened just after 1 p.m. It is unclear just how many explosions there were.

Some residents were worried about their missing cat named Lilith. After some time, the owners and Lilith were successfully reunited.

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“Anytime we have an explosion like this, the dangers are significant. We have explosive dangers due to the natural gas that is lingering within the buildings,” said Pixley. “We also have a collapse potential due to the devastation and the damage that was created by the explosion itself.”

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Xcel Energy crews were on scene to help with the investigation and to shut off the gas in the neighborhood.

“We’re working with Xcel Energy. They are assisting us not only to eliminate the natural gas potential but also the electric potential that runs through the alleys,” said Pixley.

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CBS4’s Alan Gionet was at the scene shortly after it happened.

He interviewed a witness who described the blast that was felt blocks away at Rickenbaugh Collision.

“It shook the walls over there and everything. It was bad,” said witness Brandon Stoddard.

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Santa Fe was closed from Ellsworth to 5th due to the damage and investigation. Northbound traffic was reopened just before 8:30 p.m. Fire officials say the investigation will continue Wednesday morning.

There was a natural gas explosion just one block on Nov. 22, 1996 that leveled a building at 5th and Santa Fe Drive. Five people were injured in that explosion with three hospitalized.