NEW YORK - Police are investigating reports that someone threw a lit firecracker into a subway car in Manhattan just as the Friday morning rush was ending.

Transit officials say it happened just before 9:30 a.m. in the rear car of a northbound F train at 14th Street.

Several people on Twitter said the noise sent passengers scrambling to get off the train when it pulled into 23rd Street.

"It was just chaos, it was just people running. Everybody was running away from what was going on at the time. I found out later it was a firecracker that was thrown. Some people thought it was gunshots. I honestly I'm not sure. I was just up front getting trampled by people," said one passenger who spoke with NY1 at the scene.

One woman was transported to Bellevue Hospital with a sprained leg joint.

In a statement, NYC Transit President Andy Byford said, "This is criminal, dangerous and abhorrent behavior, and we are working with the NYPD to ensure whoever did this is brought to justice."

There are no reports of any arrests.

This is a developing story. Check back for updates.