Singer Amy Winehouse was found dead Saturday at her London flat.

An ambulance service discovered the troubled performer, 27, unconscious at her home at 3:54 local time, but was unable to revive her, according to London police.

The cause of death for Winehouse, known for a defiant anthem about her unwillingness to seek drug treatment, "Rehab," was listed as "unexplained" by authorities.

The singer, also known for powerful vocals and her ability to perform in a range of music genres that included everything from R&B to soul to jazz, had a long history with substance abuse. 

In fact, Winehouse's Wikipedia page [5] has already been updated to say she died of a drug overdose -- although no one in official authority has publicly confirmed that.

According to the London Daily Mail, Winehouse had been seen with her goddaughter, Dionne Bromfield, earlier this week as the teenager performed at the iTunes Festival.

Quoting an unnamed source, the paper said Winehouse "staggered onstage" at one point and "grabbed the mic to beg the crowd to buy her protege's new album."

Winehouse had earlier cancelled a European tour following a disastrous performance in June, when she stumbled all over a stage in Belgrade -- a concert so bad, it triggered a viral-video outpouring.

Her spokesman released a statement shortly afterward, saying the singer would be sidelined until she recovered.

"Everyone involved wishes to do everything they can to help her return to her best, and she will be given as long as it takes to make this happen," the statement read. 

Winehouse had been working on a long-awaited follow-up to her multi-million-selling breakout album, 2006's "Back to Black," which won five Grammys.