MOSCOW, March 25 (UPI) -- A new criminal investigation was begun into activities of the leader of a religious doomsday sect in Russia, the country's Investigative Committee said.

The Investigative Committee spokeswoman said the probe of Pyotr Kuznetsov is based on the nearly 1,300 books belonging to him, The Moscow Times reported Tuesday.

Thirty-five of Kuznetsov's followers have been holed up in a cave near Nikolskoye since November while awaiting doomsday, which they said would occur in May. Kuznetsov has been hospitalized in a Penza area psychiatric hospital shortly after his followers moved into the cave.

The Investigative Committee office in the Penza region said a committee of psychologists and linguist found "the books contain open and concealed propaganda of religious and ethnic hatred," The Times said.

Kuznetsov was charged in November with organizing a religious group associated with violence. If convicted, he could be sentenced to two years in jail. Inciting religious hatred carries a punishment of up to four years' imprisonment.