The MTA says a female train conductor was operating a No. 7 train headed towards Hudson Yards around 5:30 p.m., when she reported not feeling well.

Investigators believe the smoke was caused by a moving train striking an object on the tracks, officials said.

but CBS News New York's cameras still caught people jumping over. "They don't seem very effective," said subway rider Keith Kelly. "I don't really understand how it discourages people because you ...