Malaysia (BBN)-A total of 139 suspected migrant grave sites have been found in 28 human-trafficking camps close to the Thai border in north Malaysia, say police.
National police chief Khalid Abu Bakar said some of the graves, found since 11 May, may contain more than one body.
They are close to where trafficking camps and dozens of shallow graves were found earlier across the Thai border, reports BBC.
Thailand subsequently cracked down on the routes traffickers used to move migrants through its territory.
The operation forced traffickers to move the migrants - who ultimately want to reach Malaysia - by sea instead.
But thousands were left stranded at sea after the traffickers abandoned them and no country would take them in.
'QUESTIONS WILL BE ASKED'
"[In] the operation which we have been conducting from 11 May to 23 May we discovered 139 of what we believe are graves," Mr Khalid told reporters on Monday.
The grave sites are hundreds of metres from the graves discovered in Thailand, he said.
Mr Khalid was speaking at a press conference a day after the government first announced the discovery of Malaysian graves. He said the biggest of the camps could have held up to 300 people.
"The first team of our officers has arrived in the area this morning to exhume the bodies," he said.
Officials are trying to determine whether the graves are of victims of human trafficking.
Earlier, Malaysia Prime Minister Najib Razak said he was "deeply concerned with graves found on Malaysian soil, purportedly connected to people-smuggling". Writing on his Facebook and Twitter accounts, he promised to "find those responsible".
The graves are evidence of a human trafficking business where migrants are kept in jungle camps while ransom is demanded from family members.
Many migrants are believed to have perished from disease or starvation.
The BBC's Jonathan Head in Bangkok says as on the Thai side, the Malaysian camps are situated in an area with a strong military and police presence, and questions will be asked about why the authorities took no action before now - action that might have saved lives.
An investigation by our correspondent has found entire communities in Thailand helping the traffickers.
ASIA'S MIGRANT CRISIS
Rohingya Muslims mainly live in Myanmar, where they have faced decades of persecution.
Rights groups say migrants feel they have "no choice" but to leave, paying people smugglers to help them.
The UN estimates more than 120,000 Rohingyas have fled in the past three years.
Traffickers usually take the migrants by sea to Thailand then overland to Malaysia.
But Thailand recently began cracking down on the migrant routes, meaning traffickers are using sea routes instead often abandoning the boats once at sea.