A woman plunged 30 feet to her death from an escalator inside the World Trade Centre transit hub while trying to grab a hat her twin sister had dropped.

Jenny Santos, 29, fell inside the Oculus hub on Saturday morning, police said.

Ms Santos, a teacher from New Jersey, was trying to retrieve a hat dropped by her twin sister while the two were on an escalator at about 5.30am when she reached too far over the railing and tumbled over the edge, a law enforcement official told AP.

Port Authority police spokesman Joseph Pentangelo said the woman was taken to a hospital where she was pronounced dead. Police are investigating.

The Port Authority Benevolent Fund tweeted: "Very sad. Our thoughts and prayers are with her family."

And a friend said on Facebook: "Very sad to hear the passing of one of the kindest, most beautiful people I have had the honour of meeting. All of my prayers and condolences go out to Jessica and Amanda an the rest of the family."