'Dabloo', a naxalite leader, in a sms to a reporter of a private TV channel, claimed that the Maoists planned to kill the chief minister, State Home Department Principal Secretary Amir Subhani said.
The message demanded the release of Naxal leaders 'Raviji' and Diren Singh.
"Director General of Police Anand Shankar and Inspector General of Police (Operations) S K Bhardwaj are probing the issue," Subhani said.
"We have tightened the security for the CM," he added.
Bihar: Maoists kill 16 over land dispute
Gujarat forms special panel to probe blasts
BIhar CM orders CBI probe into engineer's death
Top Maoist leader arrested in Jharkhand
Nitish Kumar demands stern action against MNS