An early morning explosion, caused by a small bomb and reminiscent of other mysterious blasts around New York City in the last few years, destroyed a sidewalk bench and shattered windows in a Starbucks coffee shop.
No one was injured in the blast, which happened around 3:30 a.m. EDT (0730 GMT) Monday on Manhattan's Upper East Side near the Guggenheim museum.
Investigators were looking into the similarities between the explosion and three others in the last four years, police Commissioner Ray Kelly said.
"They all happened between 3:30 a.m. and 4:30 a.m., so that's the immediate similarity that we're looking at," Kelly said. "Obviously we're going to analyze the type of explosive that's been used."