But the suspicious passenger -- and his suspicious bag -- turned out to be a dentist and his equipment, railroad spokesman Aaron Donovan said.
The delayed train was the 7:57 a.m. train from Ronkonkoma to Penn Station, he said.
No one was injured.
The railroad said a report was made to Metropolitan Transportation Authority police, who then requested the assistance of Nassau County police to investigate what Nassau police said was reported as a suspicious "device."
It was not immediately clear what type of equipment the dentist was carrying or why it seemed suspicious.