Worries reverberated across the Atlantic, where an already robust security operation was being beefed up for Wednesday’s ceremonial funeral for former Prime Minister Margaret Thatcher.

A person who spoke on the condition of anonymity to protect the family’s privacy confirmed the death of an 8-year-old boy.

Google stepped in to help family and friends of runners find their loved ones, setting up a site called Google Person Finder.

The FBI said it had set up a phone line for members of the public to call with information about the explosions.

Officials said there was no report of a specific threat to New York, but city residents were urged to be vigilant as police took both highly visible and unseen precautions.