The New York City fire department said there were at least 11 minor injuries, according to The Associated Press.
A Harlem Hospital spokesman said there was one patient so far in a "condition reported as serious trauma."
"We are expecting more" patients, spokesman Lamarr Nelson said.
The FDNY said it was mobilizing units for a three-alarm response. The NYPD would only say it was responding to an emergency.
TV news footage showed firefighters spraying a hose from a ladder truck as smoke billowed from the area.
Metro-North Railroad trains run on elevated track along Park Avenue at the point and the MTA said service on the New Haven and Harlem lines into and out of Grand Central Terminal was temporarily delayed until further notice "due to police activity."
source: newsday.com
