The world has lost a lot of celebrities. Some of them died from an accidental drug overdose, others from motor accidents, while others simply died from sicknesses like cancer. However, there are stars whose main cause of deaths remain unclear, and neither their family, fans or even authorities can't figure out what caused them. Here are some of those stars.

1. Tupac Shakur

Shakur’s death through shooting is still mysterious. According to People, it's often rumored that he was a victim of inter-gang disputes and other fingers point at hip-hop moguls Sean “Puffy” Combs and Suge Knight.

Combs denied the allegations and claimed that the story was ridiculous. Suge also denied killing the Hip Hop legend and even joked that Shakur is still alive. What confused people more were the FBI files released in 2011 which detailed that the late rapper had received death threats from a terrorist cell called the Jewish Defence League. To this date, Tupac’s murder is still unsolved.

2. Bruce Lee

Bruce Lee died when he was only 32, and he was a popular actor. According to thetalko.com, it was ruled that his death was by “misadventure.” Other narrative links to his then lover, actress Betty Ting Pei. It is said that after he complained of a headache Ting Pei gave him a painkiller known as Equagesic.

The painkiller put him into a sleep that he never woke from. There are a couple of theories linked to Lee’s death. One is that he was poisoned by Betty after Chinese gangsters sent her there for that purpose. Another one is he was eliminated by the Chinese martial arts members for exposing their secrets in his films, while the last one said that the mafia murdered him.

His death is still unsolved.

3. Amy Winehouse

Amy Winehouse was a successful British singer. According to CNN, the songstress was found dead in her home in London when she was just 27-years-old, in July 2011. During her career, Winehouse was struggling with drug and alcohol abuse. When her lifeless body was found, the doctors ruled out that she died of accidental alcohol poisoning.

Many people questioned the nature of substance abuse and the treatment for it, citing that maybe Amy could have been treated to overcome her addiction. The documentary about her life titled “Amy” was released in July this year

4. Marilyn Monroe

Marilyn Monroe’s body was found in her Los Angeles home in 1962. According to thetalko.com, it was ruled out that she died of accidental barbiturate overdose. However, it was rumored that she was dating Bobby Kennedy as well as his brother President John F. Kennedy and she was poisoned by the mafia on Bobby’s behalf. Another persistent theory states that she was killed by her psychiatrist or doctor. Nevertheless, there might be some truths about her death, that may one day be revealed.