Media playback is unsupported on your device Media caption The graves were found in an area where migrants are trafficked, as Jennifer Pak reports

New mass graves with 24 bodies thought to be those of migrants have been found in Malaysia, police say.

The graves were found in the state of Perlis near the Thai border not far from 139 grave sites unearthed in May, Perlis police chief Shafie Ismail said.

Authorities believe they may belong to migrants held for ransom in jungle camps by gangs of human traffickers.

Migrants from Bangladesh and Myanmar have left for Thailand, Malaysia and Indonesia recently.

Most of the more than 100 bodies found in May belonged to Rohingya Muslims fleeing persecution in Myanmar.

Malaysian police said the latest bodies have been sent for post-mortem examinations.

Analysis: Jennifer Pak, BBC News, Kuala Lumpur

Survivors of the detention camps have told the BBC that they were tortured and raped when they couldn't pay the traffickers, and said some died from the abuse.

The news is likely to trigger more debate on whether Malaysian officials are doing enough to stop human trafficking.

Recently, the US removed Malaysia from its list of human trafficking's worst offenders.

But, human rights groups accused American officials of doing this in order to speed up a trade pact with the Asia Pacific region, something the US has denied.

In May, Malaysian officials said a series of camps found in the jungle near Malaysia's border with Thailand showed how some migrants had apparently been held in "human cages" made of wood and barbed wire at the camps.

That discovery in Malaysia followed the uncovering of similar graves on the Thai side of the border.

After those graves were found, Thailand began cracking down on the routes used by traffickers to move Bangladeshi migrants and Rohingya Muslims from Myanmar through its territory.

Image copyright Reuters Image caption A small wooden cage found at one of the camps near Malaysia's border with Thailand

The migrants, who want to reach Malaysia, were instead being sent by sea, but thousands were left drifting as no country wanted to take them in.

Following the discovery of the sites in May, Malaysia and Indonesia agreed to stop rejecting boats and to provide temporary shelter to the migrants.

Though Thailand said it would stop towing boats away from its territory, it said it would not take in migrants.

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.

Why are so many Rohingya stranded at sea?

The Indonesian villagers saving migrants