A Maine bookmaker has admitted his involvement in an illegal betting operation that local authorities claim was the largest in state history.

This week, the US Attorney’s Office for the District of Maine announced that Stephen Mardigan had pleaded guilty to charges of running an illegal gambling business, money laundering and filing a false income tax return. Mardigan is potentially looking at a 20-year sentence on the money laundering charge alone.

The 61-year-old Mardigan was arrested in April 2017 but he’d been making book out of his Portland home since 2003, during which time he handled millions of dollars in wagers and laundered at least $4.5m through his used-car business. Mardigan used the proceeds to amass a real estate portfolio of some 30 local properties, from which he derived an annual $1m in rent.

Mardigan used his car business to process payments from gamblers, including another car dealer who lost a total of $2m to Mardigan’s book over a six-year period. Another client in Florida deposited $1.4m through Mardigan’s Avenue Auto businesss over the same span.