A post mortem examination on British singer Amy Winehouse failed to determine how she died and more toxicology tests are being carried out, with the results expected in two to four weeks, police said on Monday.

The autopsy was carried out after an inquest into the 27-year-old's death opened and adjourned.

The "Back to Black" singer, who has fought drug and alcohol addictions, was found dead at her north London home on Saturday afternoon.

As sales of Winehouse's music soared and speculation swirled about the release of a possible posthumous album, her father Mitch flew in from New York to visit a growing shrine outside the house.

Surrounded by television crews and well-wishers, he read the dozens of condolence messages and walked along banks of teddy bears, flowers -- and the occasional bottle of vodka -- left by fans of the troubled singer.

"Thank you for coming," he told the fans. "It means so much to me and my family."

A somber mood hung over Camden Square, where Winehouse lived, as a constant stream of fans arrived to lay flowers and leave messages for the singer amongst flickering candles.

Some well-wishers were unable to hold back tears as they looked in near silence at fans' tributes. Messages for the singer were left both by locals, including one saying she is "going to be thoroughly missed in Camden," and by fans from as far afield as Colombia, Mexico, Italy and Spain.

Winehouse's battle with alcohol and drugs was well-documented, most famously in one of her best-known songs "Rehab," in which she sang, "They tried to make me go to rehab but I said no, no, no."

She slid from being a chirpy teenage singer from a north London Jewish family to someone who could barely walk at her final concert performance in Serbia.

The beehive-haired soul singer won critical acclaim after the release of her debut album "Frank" in 2003 before becoming a worldwide phenomenon with the success of "Back to Black."

Winehouse's death has sparked a surge in demand for her music. British music retailer HMV predicted on Monday that she would be number one next week as sales of "Back to Black," which won five Grammys, continue to grow.

The company said many people had downloaded the album online but many would want to buy CDs to feel a "more tangible and closer connection with Amy."

"It's something that we tend to see when any great music legend or rock star passes," said HMV spokesman Gennaro Castaldo.

The Daily Telegraph newspaper reported on Monday that material recorded before Winehouse's death could be released as a posthumous album, citing sources who said Winehouse had recorded "a lot of material" and that her parents would have the final say on whether a new album is to be released.

Winehouse's spokesman told Reuters there was currently no confirmation of the release of a third album. "I know there's material about, but no one's talked about it," he said.

The inquest will resume in October.