Lawmakers in Illinois are pushing to close down the state's riverboat gambling industry, an effort that gives already jittery casino investors something else to worry about. The Illinois House passed a bill to ban riverboat casinos by a 67-to-42 margin, with seven members abstaining, the Associated Press reported Thursday. Proponents of the bill contend that the casinos fuel gambling addiction and lead to crime. The bill is seen as unlikely to succeed, however, because the president of the state Senate, Emil Jones (D., Chicago), has said he will block it. Even so, J.P. Morgan analyst Harry Curtis says the measure could stay alive until late 2006 because of legislative procedures in Illinois. The state's big riverboat operators are Boyd Gaming ( BYD), Harrah's Entertainment ( HET), MGM Mirage ( MGM) and Penn National Gaming ( PENN). Shares of all but Penn National slumped Thursday on general negative sentiment about casino stocks, which was exacerbated by several analyst downgrades earlier in the day. Penn National rallied after the company reported a stronger-than-expected third quarter.