Lee, who was informed late a year ago that her access to the country was denied, also expressed serious concern that "the repressive practices of previous military governments were returning as the norm once more" in Myanmar, describing the situation faced by civil society across the country as "increasingly perilous".
Around 700,000 Rohingya people were forced to leave their homes in the Rakhine state to escape persecution at the hands of Myanmar authorities, an act condemned by the global community as ethnic cleansing.
The UN human rights chief said last week he strongly suspected there had been acts of genocide against the Rohingyas to which Myanmar's security adviser had called for "clear evidence".
"It has. substantively contributed to the level of acrimony and dissension and conflict, if you will, within the public". This content goes viral, normalizing hate speech and shaping public perception.
Investigators also found that a certain social-media platform - it rhymes with lace hook - had a hand in helping spread hate speech in Myanmar and fuel unrest.
Government spokesman Zaw Htay said the reports presented Monday by the Independent Fact-Finding Mission on Myanmar and U.N. Special Rapporteur on Human Rights in Myanmar Yanghee Lee lacked credibility.
Lee adds that the ultra-nationalist Buddhists also have their own Facebook accounts which incite "a lot of violence and a lot of hatred against the Rohingya or other ethnic minorities".
To date, more than 650,000 Rohingya Muslims have fled Myanmar's Rakhine state into Bangladesh, with many refugees providing testimonies of executions and rapes by Myanmar's security forces.
"And I'm afraid that Facebook has now turned into a beast, (instead of) what it was originally meant to be used (for) - maybe in other parts of the world too".
"Everything is done through Facebook in Myanmar", she said.
Calls for action have grown louder since the Rohingya crisis erupted previous year, sending some 700,000 of the minority fleeing across the border since August.
"There is a blurred line between freedom of speech and hate crime", said Lennon Chang, a lecturer in criminology in Monash University.
"We have invested significantly in technology and local language expertise to help us swiftly remove hate content and people who repeatedly violate our hate speech policies", Budhraja said, adding that the company has worked with experts in Myanmar on "safety resources and counter-speech campaigns".
"Of course, there is always more we can do and we will continue to work with local experts to help keep our community safe".