The threat e-mail by suspected maoists, which landed at Orissa Chief Minister Naveen Patnaik's office here Saturday, had its server in Czech Republic, according to preliminary investigation by cyber experts.

The e-mail to cmo@ori.nic.in from PLGA@orissa.gov.in had its server in Czech Republic, Commissioner of Police B K Sharma told PTI, adding all steps were being taken to reach the sender of the e-mail purportedly sent by the Maoists.

Though the server was located in Czech Republic, the sender might have sent it sitting in the state.

The e-mail threatened to blow up Patnaik's residence and other vital installations of the state and warned the administration that the Maoists would attack Bhubaneswar, Cuttack and Puri if an anti-Maoist operation was launched.

Refusing to divulge whether the state government was contacting Interpol to find the sender, Sharma said the state government was consulting cyber experts.

Since the sender has successfully hidden his Internet Protocol (IP) address, it is difficult for the experts to know from exactly where the e-mail was sent, an official said.

"Cyber crime experts in the state and from outside are engaged in the investigation," DGP Manmohan Praharaj said.

A criminal case was registered under Section 66 A (Cyber Crime) and 66 F (Cyber Terrorism) of the Information Technology Act. A case was also registered under section 506/507 of the Indian Penal Code, sources said.