After a lengthy investigation, the US Senate has pointed out that HSBC ignored tell-tale symptoms of money laundering through its Mexico operations for several years, according to the Guardian in a report today. So far, the bank has not denied allegations.

The Senate’s investigative report says that the bank conducted business with a string of casas de cambio, or “money changing houses,” believed to double as nodes in drug-cartel networks. Facing potentially hefty fines, HSBC fired executives, re-assigned positions, and issued scores of apologies to US regulators.

The harsh fines come as little surprise to the bank’s Latin American compliance executive, Mr. John Root. In July of 2007 Mr. Root expressed concern toward the bank’s Mexico unit over what he perceived to be a malfunctioning anti-laundering committee. According to the Financial Times, analysts expect that HSBC could face fines as high as $1bn.

Across the past decade, the global bank already has two scoldings by regulators over poor money-laundering policy under its belt, but HSBC says that its new management team has already taken initial steps to fix its compliance policy.

To keep a wary eye on money laundering in the future might not be a task for HSBC only. As New York Magazine’s cool story on the Sinaloa Cartel tells us,  the US Senate investigation into HSBC’s behavior comes at a point in time when drug-trafficking across the US-Mexico border is not only booming, it is utterly complex -and getting increasingly global too. Other banks – not just HSBC – might want to check their cajones before shaking hands with a fresh client.