Nearly 13 years after the legendary James Brown died on Christmas Day, people who were close to him reveal their doubts about the circumstances surrounding his death.

Brown had apparently been struggling with a persistent cough for about a month before he finally decided to seek treatment at the Emory Crawford Long Memorial Hospital in Atlanta, Georgia. He was admitted for treatment and observation, but his condition worsened throughout the day.

While at the hospital, the Godfather of Soul suffered a fatal congestive heart failure triggered by a complications of pneumonia, including fluid in his lungs. He was pronounced dead at 1:43 a.m.

Now, at least 13 people who knew the singer well suspect that he did not die of natural causes, according to a new, explosive report by CNN journalist Thomas Lake.

Among those who believe Brown was murdered are musician Jacque Hollander and the very doctor who signed his death certificate in 2006, Dr. Martin Crawford.

Crawford believes that Brown's death may have been caused by an overdose, accidental or otherwise, because his condition "changed too fast."

"He was a patient I would never have predicted would have coded," he said. "But he died that night, and I did raise that question: What went wrong in that room?"

Of the 140 people interviewed by Lake, many suspected that Brown's manager, Charles Bobbit, may have a hand in his sudden passing.

Bobbit was by the singer's side when he took his last breath, but apparently his story of the event has changed a lot over the years. His account has always been "a little vague," and "didn't make sense."

Andre Moses White, a friend who helped the "Get Up (I Feel Like Being a) Sex Machine" singer check into the hospital, was convinced from the get-go that Brown's death was due to foul play.

He even took a vial of the singer's blood so it could be tested and used as evidence in a criminal investigation.

Since an autopsy was never performed, some of Brown's friends and family members are hoping to have one done now. They also want police to launch a criminal investigation into his death.

The CNN investigation also looked into the death of Brown's third wife, Adrienne Brown, who died in 1996 while recovering from plastic surgery.

At the time of her death, police ruled that there was no foul play, but her friends believe otherwise.

"At least three other people believe the death of Adrienne Brown was not an accidental overdose, despite what the authorities said in 1996," read the CNN report. "There are legitimate questions about James Brown's death that can only be answered by an autopsy and a criminal investigation. And there is a disturbing pattern of similarities between Adrienne Brown's death and James Brown's death 11 years later."

The mystery surrounding Adrienne's death only deepened as a confidential informant's notebook obtained by the network from the detective who was in charge of the case, Steve Miller, supports the claims.

According to the informant, who is no longer alive, a doctor confessed to giving Adrienne, 45, a fatal dose of drugs. However, the doctor has since denied the allegations.

Brown's family, including daughters Yamma Brown and Denna Brown Thomas, have refused to comment on these very serious claims. CNN also asked about their refusal to authorize an autopsy and the rumor that Brown's crypt is empty, but they've received no explanation.

You can read the full three-part bombshell report, which also touches on Brown's past and his violent tendencies, here.

What do you think of these claims about Brown's death?