There were four people on board the helicopter that crashed into the Hudson River, law enforcement sources said.

All four have been pulled from the water, though it is not clear what condition they are in.

The helicopter in the Hudson River on Thursday.via NBC News

Someone who witnessed crash said he saw one of the helicopter’s blades fly off.

Avi Rakesh said he saw the helicopter going south toward New Jersey when “the chopper blade flew off.”

“I don’t know what happened to the tail, but it just straight up dropped,” Rakesh told NBC News. “It dropped feet away from Holland Tunnel, and I can’t imagine if it hit it.”

The NTSB is gathering information on the Hudson helicopter crash.

The FDNY said that it received a call of a helicopter in the water at around 3:15 p.m. and that its units are responding to the scene.

The department’s land marine units are executing rescue operations, the FDNY said. It is still not clear whether there are injuries or how many people were on board.

Pier 40 is an active, multiuse facility along the Hudson River. There are sports fields, tourist party boats and a large car park.

It’s at the intersection of West Street and Houston Street.

The helicopter went down in the area of the West Side Highway and Spring Street, the New York Police Department said. It warned of traffic delays and emergency vehicles in the surrounding areas.

A helicopter has crashed into the Hudson River near Pier 40 in New York City.

It is not yet known if there were any injuries or fatalities. It was also not immediately clear who may have been aboard.