NEW YORK -- New details are emerging about events surrounding a dead fetus that was found Tuesday morning in an airplane toilet at New York City's LaGuardia Airport. A law enforcement source told CBS New York the fetus was left on the plane by a teenager.

The New York Post, citing a law enforcement source, reports the teen suffered a miscarriage inside the plane's lavatory.

The law enforcement source said police investigating the case are looking at sisters from Brooklyn who were traveling from Jamaica through Charlotte, North Carolina, and on to LaGuardia Airport.

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After the American Airlines plane landed Monday night in New York, one sister allegedly ran to a lavatory in the middle of the aircraft while the other sister waited outside the door, according to the law enforcement source.

A four-person crew from Airway Cleaners boarded the plane the next morning and found the fetus in the toilet.

The plane was parked by the American Airlines hangar — not at a gate — when the fetus was discovered.

Flight crew told the Port Authority Police Department about the young women in 32 A and B. Police learned their names and on a hunch called Kings County Hospital, where the teen was located. The sisters' mother had picked them up at the airport and took them straight to the hospital, the source said.

The young woman allegedly told investigators she'd been bleeding heavily for days. She also allegedly told police that while in the lavatory, she "pulled the baby out" and never heard it cry or breathe, the source said.

She claimed she didn't realize she was pregnant, the source said.

An autopsy is expected to determine if the child was born alive.

An American Airlines spokesman has called the situation "tragic and sensitive" and said they are "actively cooperating with law enforcement in their investigation."

CBS News' Kris Van Cleave contributed to this report.