Hank Williams Jr. says a spiked drink caused his problems at a weekend concert in Baton Rouge, La., and he's going to hire a private detective to find out who slipped him the mickey. A spokesman for the country singer said Williams also will take a blood test to determine if he has traces of the psychedelic drug PCP in his system. Williams was onstage only 20 minutes at the show before stumbling off and leaving behind an arenaful of very angry fans. According to the Williams camp, a man who has been harassing the singer recently was seen dropping something into Williams' drink before the show, and another Williams spokesman said something may have been added to his drink while he was in the restroom. To make up for the aborted show, Williams sent a $65,000 check to the Baton Rouge Centroplex to cover expenses and agreed to perform a benefit in Baton Rouge on May 23 for families of police officers killed in the line of duty.