Following an autopsy on Friday, the Los Angeles County Coroner's office said there was no evidence of foul play, but gave no cause for Jackson's death.
It said the results of toxicology tests could take weeks to come back.
A spokesman said Jackson had taken "some prescription medication", without specifying which.
Jermaine, who confirmed his brother's death to journalists last Thursday, was interviewed for NBC's Today programme in the grounds of the sprawling Neverland ranch, 150 miles northwest of Los Angeles.
Fighting back tears, the 54-year-old described how his mother, Katherine, had called him to break the news.
"She was crying, saying he was dead."
He added: "To hear my mother say, 'Michael is dead,' to feel and hear the tone in her voice to say her child is dead, is nothing that anyone can ever imagine."
When he arrived at the UCLA medical centre, he had seen his brother's body, he said.
"To see him there lifeless and breathless was very emotional for me.
Jackson had been due to stage comeback concerts in London
"But I held myself together because I knew he's very much alive in his spirit, and that was just a shell.
"I kissed him on his forehead, and I hugged him, and I touched him and, I said, 'Michael, I'll never leave you - you'll never leave me'."
He said he was his younger brother's "backbone" and wished he could have died instead.
"I wanted to be there for him - I was there and he was sort of like Moses.
"Things he couldn't say, I would say them - during trials, during everything."
'No viewing'
Jermaine, who appeared on UK reality series Big Brother in 2007, asserted that Neverland should be his younger sibling's final resting place.
"He created this," he said. "Why wouldn't he be here? I feel his presence."
People will be hearing a lot of that unreleased material for the first time ever. There's just some genius and brilliance in there
Tommy Mottola Former Sony Music chairman
The Jackson family, who have ruled out a "public or private viewing" of Michael's body at the ranch, are due to announce a public memorial soon.
Meanwhile, Tommy Mottola, former chairman of Sony Music - which owns distribution rights to Jackson's music - has said new releases of unheard tracks "could go on for years and years".
"There are dozens and dozens of songs that did not end up on his albums," said Mottola, who was in charge of Sony from 1998 to 2003.
"People will be hearing a lot of that unreleased material for the first time ever. There's just some genius and brilliance in there."
The material includes unused tracks from sessions for some his classic albums as well as new songs recorded with singer and producer Akon and Black Eyed Peas frontman Will.i.am.
One-Minute World News
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To hear my mother say, 'Michael is dead,' to feel and hear the tone in her voice to say her child is dead, is nothing that anyone can ever imagine
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