UPDATE: Investigators: Improperly Installed Gas Dryer Caused Rockville Home Explosion

Update, 5:35 p.m.:

Beth Anne Nesselt, a spokeswoman with the county fire and rescue service, explained in an email the change in the medical condition reported for the woman who was found, along with a man, in the rubble of this morning's home explosion on Ashley Drive in the Randolph Hills neighborhood of Rockville/North Bethesda:

"Both occupants were initially assessed on the scene as having serious/non-life- threatening injuries and were transport by land to an area trauma center. Patient status can change, sometimes rapidly, and when the unit arrived at the hospital and the patients were evaluated by emergency room staff, the female patient was determined to have serious and life-threatening injuries. The male occupant’s status did not change upon arrival at the hospital. Unfortunately, I do not have an update in regards to any changes (or upgrades) to his status over the course of the afternoon however I can confirm that the woman’s status has not changed and her injuries are considered to be serious and life-threatening."

The Gazette has video from the scene and an interview with a neighbor who said, "I'm just shocked and amazed that anybody got out of that alive."

Update, 5 p.m.:

County fire and explosive investigators announced this afternoon that they had concluded that an improperly installed natural gas dryer caused an explosion in the 11200 block of Ashley Drive in the Randolph Hills neighborhood early Wednesday morning.

An adult man and an adult woman were found under debris toward the rear of the single-family ranch style home and were taken to a local burn center.

The man remains is in serious condition and the female is in serious condition with life-threatening injuries, county fire and rescue said in a news release on Wednesday afternoon. That is contrary to earlier media reports that said her injuries were not life threatening.

The explosion caused an estimated $750,00 in damage. The home where the explosion occurred was a total loss, a fire spokesman said. Two adjacent homes also sustained damage.

Seventy-five firefighters responded to the explosion and remained on the scene for about an hour-and-a-half, the news release said.

Investigators remained on the scene for an additional eight hours and were assisted in their investigation by representatives from Washington Gas and Pepco, the release said.

"Gas appliances be installed by a licensed professional," the release said.

Update, 3:01 p.m.:

@nbcwashington reported in a tweet that the home explosion was "caused by gas leak relating to clothes dryer being converted from gas to electric."

Original post, 9:39 a.m. May 4:

A house exploded just before 3 a.m. on Wednesday in the 11200 block of Ashley Drive in Rockville, seriously injuring a man and a woman and scattering debris 50 feet in all directions, a county fire and rescue spokesman said.

Montgomery County fire and explosives investigators are investigating the cause along with Washington Gas and Pepco, said Assistant Chief Scott Graham.

The single-family ranch-style home near Boiling Brook Parkway and Schuykill Road near Garrett Park was leveled by the blast and is a total loss, Graham said.

A man and woman were found amid the debris at the back of where the home used to stand, he said.

"They were transported to  a local burn center for treatment" of non-life-threatening injuries, Graham said.

There was moderate damage to nearby homes, he said.

A neighbor told NBC 4 that the couple recently moved into the home. Video from the scene showed debris littering the street and in branches of trees.

Correction: The original post incorrectly stated the time of the explosion. The first sentence of the original post has been corrected and the time reference has been removed from the first update.