Illinois officials say a crackdown on gas station owners accused of evading state sales taxes has recovered more than $100 million.

Attorney General Lisa Madigan's office and the Illinois Department of Revenue have been part of a joint ongoing criminal enforcement operation. So far they say 50 gas station owners across Illinois have been charged. Of those owners, 40 have been convicted and some were imprisoned.

State officials say they started the effort to stop some gas station owners who they say were underreporting revenues to avoid paying taxes to the state.

A recently enacted law in Illinois established stronger penalties for businesses and retailers that evade sales tax bills. The law imposes graduated penalties based on the amount of sales taxes evaded.