Protests have been taking place across the country.
They say they'll just keep making fake accounts.
The country is accused of carry out ethnic cleansing in Rakhine state.
Tillerson said violence against the Rohingya Muslim minority showed "characteristics of crimes against humanity."
Independent observers are still largely excluded from the area and have not been able to verify the grave.
Nearly 90,000 Rohingya have sought refuge in Bangladesh in the past 10 days, fleeing the violence.
Two senior U.N. officials told Reuters the crisis is significantly worse than previously thought.
The military launched an offensive against the minority group in October.
The Myanmar army initiated a crackdown on purported Rohingya militants in October.
Ahead of Myanmar's historic elections, a new report finds evidence of ongoing genocide against the Muslim minority group.
Most are overseas and have been unable to register; canceled polls in areas affected by ethnic violence could also dent the election's credibility.
The November elections will show if Myanmar's march to democracy is real.
Almost 140 shallow graves were discovered near the border with Thailand.
Authorities don't know yet how many bodies are in each of the 139 grave sites.
Fleeing persecution, Rohingya migrants are being kept at sea by countries that don't want them.
The Rohingya, a persecuted Muslim minority in Myanmar, were among the hundreds of refugees rescued in Malaysia and Indonesia this weekend.