The New York Daily News reported a representative for the family had announced the sad news.
Entertainment Weekly said Richardson's husband, Liam Neeson, and their family released the following statement:
"Liam Neeson, his sons, and the entire family are shocked and devastated by the tragic death of their beloved Natasha. They are profoundly grateful for the support, love and prayers of everyone, and ask for privacy during this very difficult time."
Reports earlier in the day had said the film and stage star had been taken off life support at New York's Lenox Hill Hospital at about 1:30 p.m. Several media outlets had quoted unnamed sources close to her family as saying the actress was declared brain dead Tuesday.
Neeson and their two sons, as well as Richardson's mother, aunt and sister -- actresses Vanessa Redgrave, Lynn Redgrave and Joely Richardson -- reportedly had all been at the hospital with the critically injured woman.
The New York Post said Richardson's ex-husband, theater and film producer Robert Fox, as well as actress Meryl Streep and author Joan Didion, also went to the hospital to say goodbye to Richardson.
Friends of the actress told E! News a small private funeral is being planned.
Richardson appeared in the movies "Gothic," "Blow Dry," "The Parent Trap," "Maid in Manhattan," "Asylum" and "The White Countess." She won a Tony Award for her work in the Broadway revival of the musical "Cabaret."