At least 139 graves spread over 28 human trafficking camps were found by the police during Ops Wawasan Khas on May 11, The Star reported.
"We found a highly decomposed body on the ground, believed to have died two weeks ago," said Inspector-General of Police Tan Sri Khalid Abu Bakar on Monday.
"We don't know how many bodies are in the graves but exhumation works start today. We can't tell yet if they are the Rohingyas or Bangladeshis," he added.
The discovery of mass grave by the police has made clear that there were such trafficking camps on the Malaysian side of the border. These camps are likely to be set up by human trafficking syndicates.
Mass graves were also found near the border at Padang Besar earlier this month. At least 33 bodies believed to be migrants were recovered.