Federal affidavit says employees carried duffels containing bags of the drug into airport and handed them to passengers who had been through TSA checkpoints

Southwest Airlines baggage handlers took part in a marijuana distribution operation that stretched from Oakland, California, to Little Rock, Arkansas, a recently unsealed federal affidavit alleged.

Nine of the accused have been arrested, two are serving sentences for other crimes, and three are still at large.

The operation, the Drug Enforcement Agency said in its statement, allowed the baggage handlers – who weren’t required to go through a full security screening – to carry duffel bags and backpacks filled with plastic bags of the drug into the Oakland airport, where they handed them off to passengers who had already been through TSA checkpoints. The passengers then flew to cities including Little Rock and New Orleans, where they passed off the bags.

At the center of the investigation are three Southwest employees: Kenneth Fleming, 32, Michael Vindeau, 28, and Keith Mayfield, 34, all Oakland-native baggage handlers. Mayfield’s financial records “show activity consistent with money laundering”, according to the DEA.

The most important non-Southwest partner in the operation, according to the affidavit, appears to be Donald Holland, who claimed to be an account executive at Lathrop, California-based A&L Investments (investigators have cast doubt on this claim) and had a prior arrest in 2009 for possession of 2kg (4.5lb) of cocaine. The affidavit said in 2012 Holland had his Bentley Flying Spur seized after it was used to transport marijuana across state lines.

The documents set forth in the DEA statement include several photos. One picture, taken on the occasion of Holland’s 40th birthday, is said to include two of the other defendants in the case together at a Florida mansion; another of the accused conspirators, Travon Baker, allegedly posted photos of stacks of cash and jewelry to Instagram using hashtags including #drugmoney.

Southwest Airlines said that it was working with the DEA. “We are fully cooperating with authorities and will continue to work with law enforcement, airport authorities, and our security partners to perform due diligence in upholding high security standards,” wrote a spokeswoman in a statement to the Guardian.

The legality of marijuana in particular now varies so wildly from state to state that the TSA simply says it does not search travelers for drugs, though it doesn’t give them back if it finds them in the course of a screening. California, where the operation originated, has historically lax enforcement of its marijuana laws, and the laws themselves have become less strict over time.