"That the Maoists are roaming freely inside the sanctuary area was alleged by forest personnel, who boycotted the tiger census on May 8. I have already informed the state government about their allegation," Orissa's chief wildlife warden P N Padhi told PTI today.
The forest officials suspected that a large number of dreaded ultras from neighbouring Chhattisgarh had entered into the sanctuary area after the Dantewada massacre on April 6.
The fear of the forest personnel stems from the recent killing of Sangram Swain, a forest guard inside the sanctuary on April 29.
Home department must be aware if there are Maoists inside the sanctuary, said forest department secretary U N Behera.
The Sunabeda Wildlife Sanctuary, spread over 600 sq km in Nuapada district bordering Chhattisgarh, had 32 tigers according to a census conducted in 2004.
The sanctuary comprises 15 revenue villages and is home to about 15,000 ethnic tribes belonging to Chakuita, Paharia and Bhunjiya tribes.
Naxals hoisted a black flag in the sanctuary area on Independence Day in 2009.
The Maoists had in the past struck twice killing a member of anti-poaching squad Kirish Rout in Kutrabeda on the night of November 15 and former ward member of Sunabeda GP Chandar Singh Barge between Sunabeda and Gatibeda on the night of November 17 last year.
"They have warned us several times not to erect the gate at Cherechuan which had been razed by them," said a forest official.
On June 22, 2009, the ultras had demolished the forest gate and assaulted forest guard Nuapan Majhi and anti-poaching staffer Mansingh Sabaria before fleeing into the forest.
The ultras had also issued similar threats at a forest gate located on the southern side of the sanctuary at Bharuanmunda. Forest guard Jhasketan Seth reportedly received the threat, police records said.