The grisly discoveries in Malaysia followed the uncovering of similar graves on the Thai side of the border at the beginning of May
Twelve Malaysian police officials have been held on suspicion of links to people-smuggling camps where authorities have uncovered nearly 140 graves believed to hold the bodies of migrants from Myanmar and Bangladesh, a government minister said on Wednesday.
Deputy Home Minister Wan Junaidi Tuanku Jaafar was speaking the day after police forensic teams began exhuming bodies from the graves, discovered around 28 camps at six locations along a 50-km (30-mile) stretch of the border with Thailand.
"Although there are 139 graves, we have not managed to dig up all of them," he told reporters at Malaysia's parliament.
"Forensics have to do it carefully so the bodies and evidence are preserved. We don't know how many there are, and who they are."
The dense forests of southern Thailand and northern Malaysia have been a major stop-off point for smugglers bringing people to Southeast Asia by boat from Myanmar, most of them Rohingya Muslims who say they are fleeing persecution, and Bangladesh.
The grisly discoveries in Malaysia followed the uncovering of similar graves on the Thai side of the border at the beginning of May.
That prompted a crackdown by the Thai authorities on the camps - where migrants were typically held until a ransom was paid - after which traffickers abandoned thousands of migrants in overloaded boats in the Bay of Bengal and Andaman Sea.
Police and Reuters witnesses have reported signs of torture and abuse at the abandoned camps in Malaysia's northern Perlis state.
Their extent has raised questions about official complicity on both sides of the border - on Tuesday Malaysia said park rangers were under investigation and Wan Junaidi said 12 police officials had been detained on suspicion of involvement, either directly or as facilitators.
"All officials will be looked into," he said. "If there are officials who knew about this but did not take action, that is an offence. We are also looking into that angle."
The area where the camps were found is rugged and densely forested, and Malaysian authorities have requested access from the Thai side of the border, where the terrain is easier. Thailand said it would consider the request.
Malaysia says the camps were uncovered after it launched an operation of May 11, following the Thai crackdown, and Wan Junaidi denied media reports that authorities had known about the camps where the bodies were found for months.
"Those were makeshift camps, and have nothing to do with this one," he said.
He added that Malaysia was looking at beefing up security along the border.
"We suggested a wall and for the police and immigration to look into this," he said. "For now, they are looking to replace fences that have been compromised."