Marijuana plants for sale for medical use at the California Heritage Market in Los Angeles on July 11. (David McNew/Reuters)

A top federal official on Tuesday said that 105 banks and credit unions are doing business with legal marijuana sellers, suggesting that federal rules giving financial institutions the go-ahead to provide services to dealers are starting to work.

The Obama administration in February gave the banking industry the green light to offer financing and accounts to pot distributors who can legally conduct business in 20 states and the District.

Sellers hailed the decision as a step toward bringing marijuana commerce out of the shadows and into the mainstream financial system. But banking groups said the guidance did little to allay fears of doing business with companies whose products remain illegal under federal law.

At an anti-money-laundering conference Tuesday, Jennifer Shasky Calvery, director of the Treasury Department’s Financial Crimes Enforcement Network (FinCEN), praised the success of the federal rules.

“From our perspective, the guidance is having the intended effect,” she said. “It is facilitating access to financial services, while ensuring that this activity is transparent and the funds are going into regulated financial institutions.”

Calvery said the 105 banks and credit unions doing business with marijuana sellers are located in states representing more than a third of the country, but she did not provide the names of the banks or the states where they are located.

Before the guidance, banks had to notify federal regulators of suspicious or illicit activity, such as moving money from drug dealing. To address that conflict, the new rules established three categories of marijuana-related reports.

Treasury said banks could file a “marijuana limited” report that says the dealer is following the government’s guidelines, including ensuring that sales revenue does not wind up in the hands of criminal enterprises. Calvery said banks have filed 502 of those reports since the guidance was issued.

If the bank believes the dealer’s revenue is not coming exclusively from legal sales, then it has to file a “marijuana priority” report to alert regulators. There have been 123 of those reports filed, she said.

When a bank ends its relationship with a pot seller, it has to file a “marijuana termination” report, which accounts for 475 of the reports FinCEN has received since February, Calvery said.

Don Childears, president of the Colorado Bankers Association, said, “Banks are still worried about doing anything to raise concerns among their regulators, which is why we need Congress” to intervene.

Credit unions and banks are wary of running afoul of money laundering statutes by accepting proceeds from an activity considered illegal under federal laws. That has made it difficult for legal marijuana dispensers who must operate exclusively in cash, placing them at greater risk of being robbed.

“Our members that are working with the banks are being told not to talk about it,” said Taylor West, a spokeswoman for the National Cannabis Industry Association.

West said the system created by the Obama administration is “so heavy on regulation . . . it has not led to a tidal wave of openings in a way that we had hoped.” Yet, she said, it is encouraging to see more institutions starting to work with the industry.

“We still need a long-term sustainable solution and that comes in the form of policy or congressional action,” West said.