Kiersten Cerveny, right, died in what investigators think was an apparent drug overdose, sources said. View Full Caption DNAinfo/Trevor Kapp and Facebook/krickenbachmd

CHELSEA — A Long Island dermatologist and mother of three died of an apparent drug overdose after being found unconscious in a West 16th Street doorway Sunday morning following a night of partying, sources said.

Kiersten Cerveny, 38 and from Manhasset, was pronounced dead at Lenox Health Greenwich Village after she was found about 8:30 a.m. at 223 W. 16th St., near Seventh Avenue, NYPD officials said.

Cerveny, who married another dermatologist in 2009 and reports said has three kids with him, had been out on the town with some friends when she decided to go meet up with a TV producer she had known for about a year after meeting on Facebook, sources said.

The two went to the 16th Street address. The 51-year-old producer, who has worked with HBO and Michael Moore, knew another man who was subletting a third-floor apartment there and frequently hosted parties, sources said.

Cerveny and the producer spent about three hours there, sources said.

She then fell unconscious and surveillance footage shows two men carrying her into the entryway of the building, sources said.

Investigators believe the producer called 911 to report Cerveny's death before fleeing the scene and then called the hospital to check on her condition, sources said.

A man flagged down an ambulance and then took off running toward Eighth Avenue, according to Manuel Guaman, 37, who works at a nearby deli.

"They got out of the ambulance and carried her. She had on pants, but no top or shoes. She was naked and wasn't moving. Her eyes were closed. She was very white. It was scary," Guaman said.

"The guy who was waving ran toward Eighth. Nobody followed him," he added.

Cerveny had bruises around her neck, but those may have been caused by a surgery the year before, sources said.

Police are question the producer about what happened that night, sources said.

They are also still looking for the subletter, sources said.

They've also spoken with the apartment's owner, but she doesn't know the man who sublets her space very well and only knows his nickname, sources said.

There were no immediate arrests, police said.

Cerveny attended Duke and earned her medical degree from Tulane, according to her New York Times wedding announcement.

She went on to work at the Brooklyn Hospital Center and Weill Cornell Medical College, according to the Times.

"She was a darling, a lovely soul. She was delightful and always smiling. She loved her children," said a former patient, Nicole Gordon-Levine, 46.

"She was so beautiful. Her smile would light up the room," she added.

► READ MORE: Dr. Kiersten Rickenbach Cerveny Mourned by Patients and Coworkers

Former patient Victoria Albury recalled once being worried that a patch of her skin was infected, and then being moved when Cerveny, who was pregnant at the time, tried to ease her fears by touching the affected area herself.

"I said, 'You're touching my skin, pregnant and all," Albury said. "I loved her."

With reporting by Aidan Gardiner