Or is it just a prank? From Newsday:
After discovering five abandoned suitcases in various places around the city, the MTA sent out an alert to police. According to a broadcast report, authorities are concerned that terrorists may be testing various sites as possible targets.
The empty suitcases were found during the last week of March and the first week of April; one was discovered at Penn Station.
The fact that the suitcases were empty raised the alarm; genuinely misplaced bags usually have something in them. However officials also say the bags may have been scattered throughout the city as part of a prank.