WASHINGTON (AP) — A house fire that broke out in an upscale Washington neighborhood led firefighters to discover four bodies Thursday, and police and arson investigators called the blaze "very suspicious."

The fire was reported about 1:30 p.m. in a neighborhood of multi-million-dollar homes in the northwest section of the District of Columbia. Assistant Fire Chief Craig Baker said at a news conference that it took firefighters about 30 minutes to bring the blaze under control.

Neighbor Joe Carregal said he was walking his dog when he smelled smoke and went to check out what was happening down the block from where he lives.

"It was all smoke and then boom, it went to fire, coming from the second floor," he said. A man started knocking on the door but no one answered, Carregal said. Firefighters arrived shortly after and had to break down the door. They used two ladder trucks to get to the roof.

Within about 25 minutes, "we saw three people come out on stretchers," Carregal said, adding that medics were performing CPR, trying to revive the three.

The residents of the house are a family of five with two parents, a boy and two older girls, neighbors said. Carregal said the two girls were away at boarding school most of the time.

The house, a large, brick structure, is in an affluent, tree-lined neighborhood near the Washington National Cathedral. A facility for the Embassy of Belgium is nearby.

District property records list the house's assessed value at $4.58 million. The house is not occupied by the owner.

Mayor Muriel Bowser said the dead were three adults and a child. None has been identified yet, police said.

The police department is investigating the fire, Chief Cathy Lanier said. There were no obvious signs of forced entry to the home, she said, but added that it is very early in the evidence-gathering stage.

"The nature and origin of the fire is very suspicious," Lanier said. She would not explain what made the fire suspicious, however, and she would not reveal what evidence was found at the scene.

Lanier said she was not aware of any recent calls to the police from the home.

A spokesman for the Bureau of Alcohol, Tobacco, Firearms and Explosives said the agency is assisting in investigating the cause and origin of the fire.

Lanier said a 2008 blue Porsche with Washington tags DK2418 was seen at the home about 10:30 a.m. Thursday. It was found later, Lanier said, but nobody was with it. Police are asking that anyone who saw that car to contact them.

Investigators will be canvassing the neighborhood Thursday night to reassure residents and gather information, the chief said.

"Right now we have nothing to suggest this is connected to anything else," Lanier said.

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Reporters Kasey Jones contributed to this story from Baltimore and Matt Barakat contributed from McLean, Virginia.