(CNN) — One woman died and six people were hospitalized in serious condition after a major explosion in a residential area of Baltimore, according to Baltimore City Fire Department spokeswoman Blair Adams.

Three homes were reduced to rubble in the major gas explosion, Adams said.

Officials are investigating the cause, and crews are searching for people who might be trapped inside. Overhead video of the scene showed first responders searching through the rubble.

“It’s a labor-intensive rescue,” Adams said. “You have homes that were pretty much crumbled … a ton of debris on the ground, so we’re pulling and trying to comb through to see if we can find any additional occupants.”

Dean Jones, who lives a few blocks away, told CNN affiliate WJZ he was sitting on his porch when the explosion shook his house.

“It was catastrophic. It was like a bomb, like you watch things in other countries where they have, like, bombings and things like that,” Jones said. “It was like watching that in real life. Telephone poles split. I mean, houses down the block, broken glass.

“When I initially got there, I could hear a voice just saying, ‘Help.’ It’s crazy.”

Teams are working to turn off the gas main to keep the area safe, according to Linda Foy, spokeswoman for Baltimore Gas and Electric. Once turned off, the utility company will work to make repairs and try to determine what caused the explosion.

Maryland Gov. Lary Hogan said the state Fire Marshal, the Maryland Emergency Management Agency and the Maryland Public Service Commission are all helping with the recovery.

“So far, we know that the explosion has taken one life. Our prayers are with the victims and all those affected by this tragedy,” he said in a statement.

The Baltimore Sun reported last September that natural gas has been leaking out of old pipes increasingly in recent years. At the current rate, efforts by Baltimore Gas and Electric Co. to replace the pipes will take at least two decades, the Sun reported.

Last August, a gas explosion destroyed a building in a shopping center in Columbia, Maryland.

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