A U.S. Senate investigation has found, lax controls at Europes largest bank, HSBC, allowed Mexican drug cartels to launder billions of dollars, through its U.S. operations.

The extensive report on London-based HSBC Holdings PLC by the Senate Permanent Subcommittee on Investigations also says, U.S. regulators knew the bank had a poor system to detect problems but failed to take action.

The report said, HSBC executives brushed off complaints from other bank employees, so that the problems persisted for eight years.

The subcommittee released the report Monday ahead of a Tuesday hearing on the topic.

HSBC released a statement, saying its executives will offer a formal apology at the hearing.