A crane has collapsed across traffic lanes of  the Tappan Zee Bridge, which spans the Hudson River north of New York City.

All lanes of the bridge were closed in both directions after the collapse. Here's what we know so far:

-- Three northbound lanes of the Tappan Zee Bridge are about to be reopened, Cuomo said in a news conference Tuesday evening. One southbound lane is expected to reopen at about 7 p.m. and two others will reopen around 8 p.m. 

-- He said the southernmost lane sustained the most damage and it was unclear when it would reopen. He said it could be a couple of days.

-- Gov. Andrew Cuomo said late Tuesday afternoon that the main take-away was that "it was a crane doing a routine task." A construction official said the crane that fell is a new crane, but the routine task is something done thousands of time, it was either an error with the crane, an error with the hammer, or an error on the operator’s part, the investigation will determine this.

-- "We do not know why the crane collapsed. It was a new crane performing a routine task. An investigation is underway," Cuomo tweeted.

-- From Cuomo's statement: A crane that was driving piling for a new bridge failed. "We don’t know exactly what caused the malfunction. There was a malfunction that caused the vib hammer crane to collapse."

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-- "We want to do structural inspection of the bridge. Until that is done, we’re not comfortable reopening the bridge to traffic," Cuomo tweeted. He said it would take "several hours."

-- The governor said he will go onto the bridge himself during the inspection.

-- While tractor trailers are still stuck on the bridge, many of the cars have been cleared, News 12 Westchester reported.

-- The Clarkstown Town police, on the Rockland County side of the bridge, say an "extremely large volume" of traffic is expected on local roads, and it is advising drivers to "avoid the area at all costs."

-- News 12 Westchester traffic reporters said alternate routes like the George Washington Bridge, Route 59 and the Garden State Parkway were starting to see the effects of traffic being rerouted. "Avoid a 30-mile radius of the bridge," a reporter said on air. 

-- Motorists traveling southbound are being diverted at Exit 12 (West Nyack — NY Route 303 — Palisades Center Drive). All northbound traffic is being diverted at Exit 8 (White Plains — Rye — Cross Westchester Expressway).

-- The Metro-North Railroad announced Tuesday afternoon that because of the crane collapse  and closure of the Tappan Zee Bridge, a number of changes to ticketing policies and procedures are being made for the remainder of the day:
 
Metro-North’s Haverstraw-Ossining Ferry and Newburgh-Beacon Ferry will honor TAPPAN ZEExpress (TZx) bus tickets. Customers who normally depart from Grand Central Terminal  to connect to the TZx bus at Tarrytown should consider staying on the train to Ossining, where they can connect to the Haverstraw-Ossining Ferry, or should catch an express train to Beacon, where they can connect to the Newburgh-Beacon Ferry. Hudson Line tickets to Tarrytown will be honored for travel at all stations on the Hudson Line, as far as Poughkeepsie.

NJTRANSIT and Metro-North are cross-honoring Hudson Line tickets on the Pascack Valley Line.

-- South Nyack-Grandview Police Chief Brent Newbury said five injuries have been reported. The injured were two bridge workers and three people who were in cars.

-- Westchester County spokesman Ned McCormack said he's "thankful that it's only a few minor injuries. You see traffic is beginning to turn around and head away from the incident. Progress being made on clearing the bridge."

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-- The new Tappan Zee Bridge has been under construction for three years and is expected to be completed by 2018 at a cost of $3.9 billion. It is being built alongside the original Tappan Zee span, which dates to 1955.

-- In March, a 90-foot tugboat sank after it hit a construction barge near the bridge site, killing three crew members.

-- In 2013, a powerboat plowed into a construction barge at the bridge, killing a bride-to-be and her fiance's best man. The boat's driver, who had nearly twice the legal limit of alcohol in his system, pleaded guilty to vehicular manslaughter and was sentenced to two years behind bars. The victims' families, however, attributed the crash mainly to bad lighting on the barge.

--with AP