Two makeshift grenades exploded outside a building housing the British Consulate early Thursday, Election Day in Britain, causing slight damage but no injuries, officials said. A United Nations analyst found loitering nearby was being questioned, authorities said.
Officials stressed that it was not clear whether the consulate itself had been targeted. The midtown Manhattan office building houses a variety of domestic and foreign companies.
"We do not at this point have any idea who did it or a motive," Mayor Michael Bloomberg said, adding the explosion was caused by "a relatively unsophisticated explosive device." There were no threats or phone calls, he said.
The FBI and police were questioning a United Nations employee from the Netherlands who was found loitering near the building shortly after the explosion, law enforcement officials told The Associated Press. The officials, who spoke on condition of anonymity, would not say whether or not the man was a suspect.
Other officials, including one from the United Nations, confirmed that police had detained and were questioning an analyst with UNMOVIC, the U.N. commission that was responsible for eliminating Iraq's biological, chemical and long-range missile programs. The officials spoke on condition of anonymity.
As a precaution, the United Nations tightened security at its New York headquarters, calling in all its canine units and implementing other measures, U.N. spokesman Stephane Dujarric said.
The grenades had been placed inside a cement flower box outside the front door of the building.
After piecing together the shrapnel, police determined the devices were toy grenades that had been filled with gunpowder. Officers estimated that one was the size of a pineapple; the other the size of a lemon.
No timing device was used, Police Commissioner Ray Kelly said.
Investigators in white jumpsuits were inspecting the damage and looking for any evidence as to who was behind the explosions, reports CBS News Correspondent Cami McCormick.
Kelly said surveillance cameras may have captured whoever was behind it, because there was no timing device and the culprit may have been close by when the explosives were detonated.
The blasts, which Kelly said happened around 3:35 a.m., shattered a panel of glass in the building's front door and ripped a one-foot chunk from the planter.
The British consulate is on the 9th and 10th floors of the building, the mayor said. He said he expected it would be open for business later in the day.
Offices of other foreign diplomatic representatives were checked as a precaution and nothing was found, Kelly said. Security videos in the area were being reviewed, he said.
In London, a Foreign Office spokeswoman, asked whether British authorities believed the blast was terror-related, said only: "Investigations are ongoing."
"We're not speculating about whether it's connected to the election," she added. Calls to the British Embassy in Washington were not immediately returned.
The blast hit as the polls opened for what at day's end turned out to be another, who will serve a third term in office.
CBS News Correspondent Steve Holt reports that top officials in Britain have been warning for some time that election day might prove a tempting target for terrorists. But security expert Bob Strang told Holt that the explosion in New York may not be what the police were fearing.
Holt added that there's no indication of the blast affecting voting in Britain.
The 14-story glass and metal building, on 3rd Avenue at 51st Street less than a mile from the United Nations headquarters, has retail shops on the lower level.
The closure of streets around the site caused some rush hour disruptions. For a few hours, trains on one subway line skipped the stop close to the site.
In Chicago, police closed a portion of Michigan Avenue near the British Consulate for about 30 minutes to search the area as a precaution, police spokeswoman Laura Kubiak said.