Richardson was injured March 16 during a beginner's ski lesson at the Mont Tremblant ski resort in Montreal. She was later taken to the Hôpital du Sacré-Coeur de Montréal. Her husband, actor Liam Neeson, who was filming in Toronto, left the set on March 16 to be with his wife.
Richardson was flown to a New York City hospital March 17, according to CNN. Family members have been seen entering Lenox Hill Hospital in Manhattan.
The extent of Richardson's injuries have not been released, although reports in various newspapers say the situation is grave. A statement from Richardson's family is expected.
Natasha Richardson won her Tony Award for her performance in the revival of Cabaret and was also Tony-nominated for her work in the revival of Anna Christie. Her other Broadway credits include Closer and A Streetcar Named Desire.
Natasha Richardson is the daughter of actress Vanessa Redgrave and director Tony Richardson. Richardson and Neeson have two sons.