RENO, Nev. – A massive casino merger requires approval from Indiana gambling regulators .

Reno, Nevada-based Eldorado Resorts is buying Caesars Entertainment — the merger will make it the largest casino company in the U-S. Eldorado already owns the Tropicana in Evansville. The merger will add the Horseshoe casinos in Hammond and Harrison County, and the two racetrack casinos in Anderson and Shelbyville.

Current law says no one can own more than four Indiana casinos, but legislators raised that limit this year to six — the change takes effect Monday. But Gaming Commission deputy director Jenny Reske says the same law directed the commission to consider whether a purchase would create an “undue concentration of assets” with one company.

Because two of the Caesars properties are the two racetrack casinos, the 17-billion-dollar merger also requires approval from the Horse Racing Commission. And it faces a similar review from regulators in 16 other states.

Eldorado says it expects regulatory and shareholder approval to take up to a year.

The new company will keep the Caesars name.