Home Minister Rajnath Singh on Thursday said the central government cannot ask the CBI to probe the killing of woodcutters in Andhra Pradesh as the state has not asked for it."CBI inquiry can be set up only after the state government asks for it. We are helpless because the state government has not asked the centre to set up an inquiry," Rajnath Singh said in the Rajya Sabha.The home minister said some public interest litigations (PILs) have been admitted in court."There is a PIL, if the court gives an order, state will be bound to constitute a probe," he said.Twenty woodcutters from Tamil Nadu, allegedly found felling red sanders wood, were killed by police in the Seshachalam forest at the foot of the Tirumala hills.