The mystery surrounding the disappearance last month of a 22-year-old Syosset woman has ended with the discovery of her body in a car, police said Tuesday.

Jasmine Joseph's family identified her body, which was found Monday night near Jericho Turnpike and Cedar Street in Syosset. An autopsy will determine the cause of death but police suspect Joseph committed suicide.

"She had inhaled a noxious substance," Insp. Kenneth Lack told reporters Tuesday.

He declined to say what the substance was and whether Joseph left a suicide note.

Joseph's body had been in her car for an "extensive period of time," Lack said.

Passersby would not have been able to see her body in the car because she was "wedged between the front and back seats," Lack said.

Police had been looking for her since issuing a missing persons release to the news media Feb. 28.

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Relatives of Joseph were stunned at the news that authorities suspect she took her own life. Her father, Sony Joseph, an electronics technician with the Metropolitan Transportation Authority, said his daughter "would never do something like that. . . . She's very happy. . . . We are going to ask police for a further investigation."

Joseph said the parking lot where his daughter's body was found is near their home. He and other family members checked it Friday and Saturday.

"We didn't see any car there," he said.

Lack would not respond to the father's comments but said police are still investigating.

The family gathered to pray at their Syosset home yesterday. They had set up a Facebook page and distributed fliers that showed pictures of a smiling Jasmine Joseph. Simi Jawandha, 22, of Syosset, a friend, said: "We're in such a state of disbelief. . . . She was incredibly happy, full of life."

Joseph had last called her parents on Feb. 24, police said.

Last week, Joseph's parents said they paid for their daughter to enroll in a nursing program at New York Institute of Technology for the 2013 fall semester -- and believed she was in the library there when they last spoke to her.

University officials said Joseph hadn't been a student at the Old Westbury school since May.

With Ellen Yan