Malaysian police say they have found 139 graves believed to hold the remains of migrants near the Thai border.
Local media had previously reported over the weekend that 30 large graves had been found in two locations in the northern state of Perlis, which borders Thailand.
Officials gave further details to reporters on Monday, saying that 28 abandoned human trafficking camps - one big enough to hold 300 people - had been found during their investigation, which was carried out from May 11 - 23.
Police said 139 graves had been found near the camps, but added that they did not know how many bodies were inside the graves. Some graves were believed to hold more than one person, officials said.
Al Jazeera's Florence Looi, reporting from Perlis state, said police had found traces of food at some of the migrant camps, indicating that they may have been recently abandoned.
"Police found one highly decomposed body and believe that person may have died two or three weeks ago," she said.
Dozens of suspected human traffickers have been arrested by Malaysian police during the investigation and officials said the information they provided has led to the graves and camps being found.
Northern Malaysia is on a route for smugglers bringing people to Southeast Asia by boat from Myanmar, most of them Rohingya who say they are fleeing persecution, and people from Bangladesh seeking work. Smugglers have also used southern Thailand.
More than 3,000 migrants, most of them from Myanmar and Bangladesh, have landed on boats in Malaysia and Indonesia this month after a crackdown on trafficking in Thailand.
Malaysian Prime Minister Najib Razak on Thursday pledged assistance and ordered the navy to rescue thousands adrift at sea.
Source: Al Jazeera