(Updated with stock prices at the close.)NEW YORK ( TheStreet) -- Shares of casino operators -- specifically those with locations in Macau, China -- were in the red Thursday on fears of a tightening of travel restrictions in the region. While earlier this week it was believed that restrictions would actually benefit Macau casino operators, making it harder for competition to enter the market, a new rule tightening visa restrictions could actually hurt revenue. Currently the policy allows residents from the Guangdong province -- the largest source of tourism -- to visit Macau once a month. But, according to multiple reports, there are murmurs that a new rule could be issued that allow Guangdong residents to visit Macau every other month. Macau is the only place is China where gambling is legal, and stricter traveling restrictions could damper revenue there. In September, Macau reported that gambling revenue had more than doubled, making it a profitable area of growth for casino operators that are having trouble in the United States amid the economic downturn. Shares of casino operators plunged earlier on the news, but recovered slightly by the end of the day. Wynn Resorts ( WYNN) tumbled 3.2% to $64.98 and Las Vegas Sands ( LVS) tanked 5.6% to close at $16.93. -- Reported by Jeanine Poggi in New York Follow TheStreet.com on Twitter and become a fan on Facebook.