Operator and supporters of marijuana dispensaries say banks are turning away their businesses because they risk falling afoul of anti-money-laundering and drug-trafficking laws.

Sue Harank, co-owner of Denver-based dispensary Alpine Herbal Wellness, said her accounts were closed in two banks and the credit union, after she opened a shop in March 2010.

Both banks and the credit union pursued our business initially and said they had talked to the corporate office and run it through legal, but a month or two later they all reversed themselves, she said.

The largest U.S. bank, Bank of America Corp, said it started withdrawing services from dispensaries after receiving a warning from the U.S. Drug Enforcement Administration in late 2007 or early 2008.