British Petroleum blames itself, a series of failures and other companies' workers for the series of events that led to the biggest oil spill in U.S. history.

The oil company released a 193-page internal report, Wednesday, detailing the causes of the deep water rig explosion in April.

The report spreads the blame between BP, the rig's owner Transocean and the cement contractor Halliburton.

Some aren't satisfied by the report.

"This report is not BP's mea culpa," said Rep. Edward J. Markey, D-Mass., a member of a congressional panel investigating the spill. "Of their own eight key findings, they only explicitly take responsibility for half of one. BP is happy to slice up blame, as long as they get the smallest piece."

Investigators are still analyzing why a key piece of equipment on the rig -- the blowout preventer -- did not cut off the flow of leaking oil as it should have.

Government investigators and congressional panels are also looking into the cause.

Members of Congress, industry experts and workers who survived the rig explosion accuse BP's engineers of cutting corners to save time and money on a project that was 43 days and more than $20 million behind schedule at the time of the blast.