Part of the area at New York's Penn Station that was sealed off Friday morning has reopened, but another section remains closed.
Workers in hazmat suits, National Guardsmen and police with dogs are at the transportation hub beneath Madison Square Garden. They're investigating what appears to be a red suitcase.
An Amtrak official says only that there's "a police situation" there.
One of the main entrances was closed off with yellow crime scene tape and a portion of the concourse above the tracks was also sealed to the public.
The station itself has remained open through the investigation.
City officials Thursday said that an FBI source warned that militants planned to bomb the subway system.