Michael Jackson's concert promoter has demanded "answers" from the late star's doctors.

Randy Phillips, CEO of AEG Live, who were staging his 'This Is It' 50-date London residency, wants to see the results of medical checks taken by the 'Thriller' star - who died of a suspected cardiac arrest last Thursday (25.06.09).

Michael was passed fit to perform and then died suddenly, amid rumours of a painkiller addiction.

Randy said: "Maybe they didn't do a good enough job. We want answers. We have poured millions of cash into Michael's comeback.

"All the tests pointed to him being in fine physical shape. It's a complete mystery. The insurance company had an independent physician fly out from New York and give him a five-hour exam.

"We were told he passed with flying colours. Now I would like to see the results. If he was taking that amount of prescription drugs, wouldn't that have been picked up in a blood test?"

It is believed that the stringent medical included over 50 different checks and tests. As a result of Michael being passed fit, AEG Live secured insurance cover for the first 22 concerts but were unable to convince insurers to cover the full 50 shows at a cost of £300 million.

The promoters now face multi-million pound payouts to ticket-holders.

Randy added: "We must know the results. I don't know what our legal rights are."

Randy also spoke about his final conversation with the singer, at rehearsals the night before he died.

He told Britain's Daily Mirror newspaper: "He did a three-hour rehearsal and we all finished up at 12.30am on Thursday morning. He was really excited.

"He was super-charged and did a group hug with the director Kenny Ortega and his manager. He was like a kid in the candy store - he was so up for it.

"I walked him out to the car and he put his arm around me and, speaking softly like he always does, he said to me, 'Do you know what - we are here, we are going to make it. I love you for doing this and now I know I can do it.' "

Meanwhile, it has been claimed Abba are set to perform at some of Michael's

O2 arena concert dates.

The quartet have so far resisted offers to reform following their split in 1983, but AEG Live are hoping to get them to sign up to take on several of the vacant dates.

David Campbell, chief executive of AEG Europe, said: "There's a little foursome out in Sweden we keep talking to."

A source close to the 'Super Trooper' hitmakers warned a comeback would be tricky.

The insider said: "There are millions on the table. But there are many hurdles to overcome."