An explosive device caused minor damage to an empty military recruiting station in Times Square early Thursday, shaking guests in hotel rooms high above.

Police blocked off the area to investigate the explosion, which occurred at about 3:45 a.m., shattering the station's glass entryway. No one was injured.

"If it is something that's directed toward American troops, then it's something that's taken very seriously and is pretty unfortunate," said Army Capt. Charlie Jaquillard, who is the commander of Army recruiting in Manhattan.

He said no one was inside the station, where the Marines, Air Force and Navy also recruit.