Wynn Resorts and Las Vegas Sands tumbled in premarket trading, after dropping roughly 10% on Tuesday, as Macao began a 45-day period of considering tighter regulations on the gaming industry. Those U.S. casino stocks have operations in the Chinese special administrative region. Officials in Macao said they want “sustained and healthy development” in the world’s biggest gambling hub. However, investors are worried about potential changes. Hong Kong-listed shares of Wynn Macau and Sands China tanked about 30% overnight.