Las Vegas' bright lights appear to be dimming some, prompting analysts to downgrade casino operators, which sent investors scurrying from casino stocks. At least two brokerages issued downgrades Thursday, while a third made cautious statements and lowered earnings estimates because room rates in the gaming mecca aren't growing as fast as they once were. Susquehanna Financial downgraded Caesars Entertainment ( CZR) to neutral from positive, citing increased competition, while Buckingham Research downgraded MGM Mirage ( MGG) to neutral from accumulate, saying the second half of the year would not be as strong as the first. J.P. Morgan lowered earnings estimates on MGM's merger partner Mandalay Resort Group ( MBG )because growth in revenue per available room, a key metric called revpar, is slowing. (All three brokerages do and seek to do business with the companies covered in research reports.) "Our forward room rates surveys in Las Vegas indicate a pause in the 10%-to-15% pricing power seen in the first half of 2004," wrote Harry Curtis, analyst at J.P. Morgan, in a note. "Operators such as Mandalay and Caesars show flat to slightly lower call-in rates in the third quarter." In reaction, the entire sector slumped, with the Dow Jones Casino Index falling 2.3%. Caesars lost 54 cents, or 3.9%, to $13.48; MGM dropped $1.98, or 4.4%, to $42.91, while Mandalay fell 3 cents to $68.62.