Tamil Nadu's ruling AIADMK party is heading into yet another political crisis. Deputy Chief Minister O Panneerselvam on Friday had to fend off serious corruption charges that inconveniently come just ahead of the closely-watched RK Nagar by-election, lending ammunition to the opposition. A report by the magazine The Week has claimed that Mr Panneerselvam, popularly called OPS, was on the payroll of sand mining baron Sekhar Reddy. The DMK has sought a CBI probe. "Only a CBI probe can bring the truth," the party's working president MK Stalin said, demanding that the ministers quit their posts till they get a clean chit.