UPDATE 2 - 29 injured in NYC explosion

ADDS DETAIL ON DEVICE FOUND ON 27TH STREET

NEW YORK (AA) – Twenty-nine people were injured in an outdoor explosion late Saturday in New York City, Mayor Bill de Blasio told reporters.

One injury resulting from the explosion at around 8.30 p.m. (1230GMT) at 131 West 23rd Street in the Chelsea neighborhood of Manhattan "might be considered serious", de Blasio said.

The cause remains unknown.

Authorities believe it was intentional but have not found any link to terrorism, he said.

Authorities are treating nearby 27th Street between the 6th and 7th avenues as a second site, but declined to give further details.

Local media report, however, that officials might have found a pressure cooker device there, similar to the one used in the Boston Marathon bombings in 2013 that killed three people and injured hundreds.

Earlier Saturday, Republican presidential candidate Donald Trump reacted to the explosion during a rally in Colorado, calling it a "bomb".

"I must tell you that, just before I got off the plane, a bomb went off in New York and no one knows exactly what's going on," Trump said. "We've got to get very, very tough," he added.

His rival, Hillary Clinton, did not comment but her campaign said she was informed of the developments.

Clinton and Trump live in New York.

There is intense police activity in the area, with closures on nearby roads and subway stops.

Officials said there was no immediate connection between the Chelsea blast and a pipe bomb explosion in Seaside Park, New Jersey, earlier Saturday, which forced the cancellation of a charity run.

That blast caused no casualties.