By Gina Cherelus

NEW YORK (Reuters) - A major New York bridge has partially reopened following a crane collapse that injured four people on Tuesday, and the cause of the accident is being investigated, state and county officials said.

The crane, used to lift concrete piles in the $4 billion replacement of the Tappan Zee Bridge, fell around noon and has been removed, officials said. The state's longest bridge connects New York City's densely populated suburbs of Westchester and Rockland counties, and carries more than 130,000 vehicles per day.

Four people suffered minor injuries, James Allen, director of communications for Governor Andrew Cuomo, tweeted. "1 worker + 3 ppl in 2-car fender bender that occurred while avoiding crane," he said, correcting earlier reports that five people were injured.

"We do not know why the crane collapsed. This is the first accident we had," Cuomo said at a news conference. "If there's a silver lining in this situation it was that no one was seriously hurt."

All northbound lanes were reopened to avoid heavy rush hour traffic on Tuesday evening, and two southbound lanes will operate by 8 p.m. ET (0000 GMT), he said. One badly damaged southbound lane will remain closed, he added.

The crane was one of 28 used in the construction of a new bridge that would replace the original which opened in 1955.

Construction began in 2013 and is expected to be completed by 2018, according to the website of Tappan Zee Constructors.

Cuomo said the collapse likely would not delay the project.

(Additional reporting by Laila Kearney; Editing by Richard Chang)