A group of Massachusetts residents opposed to casinos are challenging the sale of state property to Wynn Resorts with a new lawsuit.

The complaint filed in Superior Court on Monday asserts that the Massachusetts Bay Transportation Authority failed to comply with the state's public bidding law when it proposed selling some $6 million worth of land to Wynn for its $1.7 billion casino project in Everett.

Among the over 24 Massachusetts taxpayers who filed the lawsuit are some activists involved in the 2014 ballot question that asked voters to repeal the state's casino law. The referendum was defeated and the casino law remains in effect.

The MBTA declined to comment on the lawsuit. Wynn says the land deal followed a "clear and open" public bid process.