Security was stepped up throughout New York City on Tuesday after explosions at the airport and subway system in the Belgian capital of Brussels killed more than 30 people and wounded about 200.
"The New York City Police Department is closely monitoring the situation in Belgium and is in close contact with our international partners and with the FBI," the NYPD said in a statement.
The agency said there was "no known indication that the attack has any nexus to New York City," but that it was deploying additional counterterrorism units to crowded areas and transit locations across the city "out of an abundance of caution." The Port Authority Police Department also increased security at the area's three major airports: John F. Kennedy, LaGuardia and Newark Liberty. It also employed high visibility anti-terrorist patrols throughout the PATH system and the World Trade Center site.
Belgium raised its terror alert to the highest level, diverting planes and trains. Belgium's interior minister says authorities knew that some kind of extremist act was being prepared in Europe but that they were surprised by the scale of the attacks in Brussels. Belgian federal prosecutors say a house search in the Brussels neighborhood of Schaerbeek has "led to the discovery of an explosive device containing among other things nails."
Investigators also found chemical products and an Islamic State flag.
Their statement said that ISIS had claimed responsibility for the attacks in Brussels via a press agency, but that this information still needs to be verified.