Four people were found dead in a Floral Park, Queens, home Friday afternoon in an apparent carbon monoxide poisoning after a car was left running in the attached garage, police said.

Police described the victims as a married couple, a close friend and an upstairs tenant. The deaths are believed to be accidental.

The victims were discovered shortly after 3 p.m. when a relative of the couple came to the two-story home on 86th Avenue, near the Nassau County line, to check on them, police said.

"It looks like they all sustained carbon monoxide poisoning," a police source said.

A law enforcement official identified the relative who made the discovery as the couple's son, Robert Hugel, an NYPD sergeant.

Police identified the couple as Jerry Hugel, 83, and Marie Hugel, 80. Close friends said the couple owned the home.

Police identified the tenant who lived on the second floor of the home as Gloria Greco, 70. The fourth victim, a 76-year-old man, was not identified by police Friday night pending notification of family members.

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An investigation into the deaths was underway. The bodies showed no signs of trauma, police said. It's unknown how long the people were dead before the bodies were found.

NYPD investigators said Jerry Hugel was found in the garage, next to a parked Buick that was still running.

Police said Marie Hugel was found in a kitchen basement area off the garage. The friend was found in the first-floor living room of the home, and Greco was found in a first-floor doorway, he said.

Jerry and Marie Hugel were longtime members of a Bavarian dance club that meets Wednesdays at the Plattduetsche Park Restaurant in Franklin Square, according to friends.

"They were a lovely couple, very big in the German community," said a shaken Michael Mattern, president of the group, GTEV Schlierachtaler Stamm.

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Mattern said he called club members to inform them of the deaths. The group participated in dance competitions in Philadelphia, Washington, D.C., Vancouver, British Columbia, and elsewhere.

Hugel was the group's president for 41 years, until 2013. His wife selected outfits for the performances and the couple's children were also involved, members said.

"They did everything that had to be done, whether it was setting up for a dance or cleaning up afterward," said Kathy Fetzer of East Rockaway.

Jerry Hugel was fit enough to keep up with the younger male dancers, said Agnes Kramer, 78, of Maspeth, Queens, a friend for 50 years.

"Every week when we had practice, he was still dancing," she said. "He was slim and trim and had lots of energy."

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Hugel emigrated from Germany as a child with his parents; his wife's family hails from Austria, Kramer said.

The Hugels were married for about six decades and raised five children. The couple visited Germany several times a year and had a trip planned for the end of this month, Kramer said.

Elisabeth Hlawaty, 80, of Elmont, who came to the Floral Park house after hearing of the tragedy, recalled how Marie Hugel typed her children's college term papers.

"She was very involved; very family conscious," Hlawaty said.

The couple welcomed friends at their Cape Cod-style home -- often on short notice. "You didn't have to call them, you just rang the bell," Kramer said.

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Stunned friends and neighbors gathered outside the home Friday afternoon. Helga Harter of Bellerose, Queens, who has known the couple for 40 years, hugged Robert Hugel at the scene.

"I'm still in shock -- biggest shock of my life," she said.

Valerie Vallorani, a neighbor, said she would sometimes see the couple gardening and wave hello. "This is mind-boggling," she said.

It's unclear if the home had carbon monoxide detectors, which are required in New York City for most homes. The deadly odorless and colorless gas is created when some fuels are burned.

Mark Weprin, a city councilman who represents the area, said in a statement that he was "deeply saddened" to learn of the deaths. "It is my hope that this tragedy sheds light on the importance of having, and maintaining, a carbon monoxide detector in all homes and apartments," he said.

In 2000, six people died of carbon monoxide poisoning while sleeping in a Roslyn Heights home with a disabled detector.

The U.S. Centers for Disease Control reported 5,149 deaths from unintentional carbon monoxide poisoning between 1999-2010, an average of 430 a year.

With Anthony M. DeStefano