Story highlights Reporting on Myanmar has become more and more difficult since the anti-Rohingya crackdown began

Multiple journalists have been detained and threatened with arrest

(CNN) Myanmar has banned a United Nations official investigating the ongoing crackdown in Rakhine State from the country, after claiming a previous report by her was biased and unfair, the UN said Wednesday.

Yanghee Lee, UN Special Rapporteur on the situation of human rights in Myanmar, was informed Wednesday all access to the country has been denied and cooperation withdrawn for the duration of her tenure, the UN said in a statement.

"I am puzzled and disappointed by this decision by the Myanmar government," Lee said. "This declaration of non-cooperation with my mandate can only be viewed as a strong indication that there must be something terribly awful happening in Rakhine, as well as in the rest of the country."

Myanmar government spokesman Zaw Htay told CNN Lee "is not impartial and objective when conducting her work, there is no trust in her."

The ban came a day after Myanmar state media reported that a mass grave with 10 bodies inside had been found at Inn Din, north of Rakhine state capital Sittwe. Photos published by the military showed the grave being exhumed and multiple skeletal remains.