AEG Live, the group behind a long series of concerts Michael Jackson was to perform in London from next month, expressed its condolences to the late singer's family on Friday and said tickets would be refunded.

"On behalf of the entire AEG organization, we extend our deepest condolences to Michael Jackson's family and friends during this tragic time," it said in a statement.

"Full ticket refund information and procedures will be released next week for all Michael Jackson "This Is It" shows. Fans are advised to hold onto their ticket vouchers/proof of purchase."

AEG Live had scheduled a punishing series of 50 concerts at London's O2 Arena beginning on July 13, with an estimated 750,000 tickets sold at a price of 50-70 pounds ($80-$110) per ticket. Originally, only 10 concerts were planned.

The company is reported to have invested $20-30 million on the production already, not including any advance to Jackson.

The group's financial exposure will depend partly on how well insured it was for the multi-night run. British press reported that some insurers had turned down the opportunity to underwrite the events because of the risks involved.

AEG Live is a subsidiary of Anschutz Entertainment Group.

Media reports have suggested that AEG Live's total potential liability from the concerts could amount to 300 million pounds.

Company representatives in Europe could not be reached for comment.

Some of the original tickets sold have been sold on via eBay and other auction sites for much greater sums than the tickets' face value. People who bought from unauthorized sellers may not be covered for the costs, ticketing experts have said.

One pair of "VIP" passes to the opening show was offered on eBay for 16,000 pounds.