Two people were seriously hurt Tuesday morning after a propane explosion at a house that serves as the office of a landscaping company in Montgomery County.

       Montgomery County fire officials said on Twitter that the blast happened around 8 a.m. at the office in the 23600 block of Laytonsville Road. The head of the Montgomery County Fire Department said two people had life-threatening injuries.

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       Emergency responders rescued at least one person from the debris of the partially collapsed house. That person suffered traumatic injuries and was taken by helicopter to a hospital, fire officials said.

       The exact cause of the explosion is under investigation.

       Montgomery County Fire Chief Scott Goldstein said it appeared the explosion came from the propane that supplies heating and hot water at the building. He said two people were outside the building at the time of the blast, and one of them was taken to a hospital for life-threatening injuries. The other person, he said, refused treatment.

       Goldstein said one of the people who was hurt got to the building around 7 a.m., smelled gas and notified the local utility provider, and warned other employees to stay away from the building. Goldstein said the utility provider was on the scene when the explosion happened.