In the wake of Michael Jackson's death on Thursday, concert promoter AEG Live faces the daunting task of refunding $85 million in ticket sales for the 50 sold-out concerts lined up for this summer in London at the O2 Arena.

According to the Los Angeles Times, AEG had invested a reported $20 million in production costs for the shows, billed as the "This Is It" concerts, which were scheduled to begin on July 13. AEG's profits for the concerts were expected at around $115 million, with a three-year worldwide tour also planned that could have grossed $450 million.

In a statement released Friday afternoon, AEG President & CEO Randy Phillips said, "Yesterday was a day I will never forget, or want to remember. Michael was both weak and strong, clever and kind, talented beyond belief and equally insecure. He was a doting father, respectful son, loving brother, and caring uncle. He was my friend. I take great solace in the pride and confidence he exhibited during production rehearsals on Wednesday night. That is the memory I will cherish for the rest of my life."

Despite rumors that Jackson had been falling ill, a source close to Jackson told MTV News, "Michael has been in rehearsals. He's been in good spirits. He's been rehearsing eight hours a day for the London concerts."

Though some sources said that Jackson had been making regular visits to a Beverly Hills medical center, according to E! Online, Jackson passed a medical exam required for AEG to obtain insurance from Lloyd's of London for the shows.

"He passed the physical and everything was a go," a source tells the site, adding he was scheduled to undergo another physical before the shows. In May, Phillips said that he had "passed it with flying colors."

Phillips told the LA Times in May that Jackson was working with choreographer Kenny Ortega (the director of "High School Musical") to create a new dance move that would eclipse Jackson's signature moonwalk for the London shows.

"This was the most exciting collaboration of my life with a man who has inspired me like no other," Ortega told The Associated Press. "This was the world's greatest performer and the world will miss him."

Illusionist Ed Alonzo, who recently worked with Britney Spears on her tour, was also preparing to work with Jackson on the shows. "I've been there the last few days and was there with Michael last night while he rehearsed, and sang, and danced, and was amazing," Alonzo said on Thursday. "He was just strong and positive. ... If he had any kind of sickness or anything going on, it was well hidden. But he was always thin."

MTV will be paying tribute to MJ throughout the weekend with music videos, exclusive performances and calls and tweets from celebrity admirers and friends. For everything we've got on the life, career and passing of the legendary entertainer, visit "Michael Jackson Remembered."

Share your Michael Jackson memories by uploading video and comments to Your.MTV.com or joining the discussion below.

[This story was originally published at 10:30 am E.T. on 6.26.09]