Fans and colleagues are paying tribute to actress Natasha Richardson, who died Wednesday after falling at a Quebec ski resort earlier this week. (Peter Kramer/Associated Press)

British actress Natasha Richardson's death this week was caused by a blunt impact to the head, according to the New York City medical examiner's office.

The agency conducted an autopsy on the actress, who died Wednesday after falling while at Quebec's Mont Tremblant ski resort two days earlier.

Ellen Borakove, a spokeswoman for the office, said Thursday the death was ruled an accident, and the cause of death was an "epidural hematoma due to blunt impact to the head."

An epidural hematoma is a blood clot under the skull caused by a blow to the brain.

Funeral arrangements for the 45-year-old actress will be handled by the Greenwich Village Funeral Home.

Fans, friends shocked at death

"It defies belief that this gifted, brave, tenacious, wonderful woman is gone," said Sam Mendes, who directed the stage and screen star in her Tony Award-winning turn in Cabaret on Broadway in 1998.

New York theatres will dim their marquee lights before Thursday evening's shows get underway, in tribute to Richardson.

"The Broadway community is shocked and deeply saddened by the tragic loss of one of our finest young actresses, Natasha Richardson," said Charlotte St. Martin, executive director of the Broadway League, the trade organization representing the city's theatres and producers.

"Her theatrical lineage is legendary, but her own singular talent shined memorably on any stage she appeared."

Delay in hospitalization

The prominent actress sustained what initially appeared to be a benign fall during a private ski lesson on a beginner's slope at Quebec's Mont Tremblant ski resort on Monday afternoon. Yves Coderre, director of operations at a local ambulance company, told the Globe and Mail that paramedics arrived at the mountain 17 minutes after receiving a 911 call, but Richardson sent them away.

Though at first she appeared fine, about an hour later Richardson complained of feeling unwell. She was transported to a local hospital by ambulance and arrived there nearly three hours after the initial 911 call, the newspaper reported. She was later transferred to Montreal, where her husband, actor Liam Neeson — who had been on a film set in Toronto — joined her.

The condition is called "talk and die," because a patient may feel fine after their injury, but within hours, a blood clot forms and cuts off circulation in the brain.

"It's a fairly rare event for the vast majority of the hundreds and hundreds of head injuries that we see," said neurosurgeon Simon Walling of Dalhousie University in Halifax. "But we do recognize that it happens, and it has such tragic consequences if it's not recognized quickly."

On Tuesday, Richardson was airlifted to New York, where the couple lived with their sons, Michael and Daniel.

"Her loss alone is a horror," entertainment reporter Jeanne Wolf, who has regularly interviewed Richardson and members of her family over the years, told CBC News from Los Angeles on Thursday morning.

Given the extremely private nature of her husband, the intense media coverage the family has endured over the past few days must have added tremendously to their pain, she added.

The 81-year-old filmmaker Ken Russell, who directed Richardson in the film Gothic, described her as "always poised, prepared, focused and very, very bright" in a tribute in the British newspaper the Times.

"She was one of the few modern actresses who was as smart as she was pretty and as gentle as she was fierce."

In her blog, actress Jane Fonda recalled meeting Richardson as a young woman on the set of 1977's Julia, which starred her mother, British acting legend Vanessa Redgrave.

"She was a little girl but already beautiful and graceful. It didn't surprise me that she became such a talented actor," Fonda wrote. "It is hard to even imagine what it must be like for her family. My heart is heavy."

Celebrated by theatre community

Though she starred in a host of films over the years, including the film adaptation of Margaret Atwood's The Handmaid's Tale, Richardson was perhaps most celebrated for her stage career.

The theatre community praised Natasha Richardson, left, as the latest talented member of the Redgrave acting dynasty. The actress is seen here in 2000 with her acclaimed mother, Vanessa Redgrave, centre, and younger sister, fellow actress Joely Richardson. (Michel Eule/Associated Press)

Tributes poured out from the British and North American theatre community for the actress, praising her many accomplishments and saying she represented the latest talented generation of the Redgrave acting dynasty.

From the very beginning, when Richardson decided to follow in the footsteps of her mother and aunt Lynn to study at London's prestigious Central School of Speech and Drama, "she wanted to do it very much on her own," Gavin Henderson, the school's principal, told CBC.

She applied to the facility as "Miss Richardson" and did not reveal her family ties so that "she shouldn't seek any kind of advantage," he said. "That's how she made her way."

Her mother was also complicit, he added, pointing out that as parent and guardian, Redgrave signed her name as "Mrs. V. Richardson" on the application (her father was director Tony Richardson, who died in 1991).

Tim Walker, theatre critic for the Sunday Telegraph, also said that the actress never rested on her family's laurels.

"[Richardson's family] are a phenomenal dynasty and each of them has their own talents. You can't really lump them together," Walker wrote.

"As a stage actress she was really coming into her own, she was becoming a major star and taken extremely seriously on the stage."

British actress Judi Dench, who also attended the Central school, hailed Richardson for "an incredibly luminous quality, that you seldom see, and a great sense of humour," in an interview with the BBC.

"It's just so shocking, really shocking, and I hope that everybody leaves the family quietly to somehow pick up the pieces," Dench said.

"She was a wonderful woman and actress and treated me like I was her own," said Lindsay Lohan, who as a preteen starred with Richardson in a remake of The Parent Trap in 1998.

"My heart goes out to her family. This is a tragic loss."

Fans of the actress have flooded internet sites with their condolences, tributes and discussions of their favourites of her many film, television and theatre roles.

Richardson's death has also revived a debate over helmet laws. The actress was not wearing a helmet while taking her ski lesson, a Mont Tremblant spokeswoman said on Tuesday.

In a statement released Thursday, the ski resort extended condolences to Richardson's family and said it would co-operate with any future investigation regarding Richardson's death. The release also said its officials would not have any further comment on the incident.

With files from the Associated Press