BANGKOK (Reuters) - Twenty-six bodies exhumed at a mass grave near a suspected human trafficking camp in southern Thailand do not bear signs of violent death, police said on Sunday, following initial forensic examinations at the site.

Dozens of police and rescue volunteers trekked into the mountains on Saturday to a jungle camp in Songkhla province that authorities have linked to human trafficking and dug up 21 bodies.

Five bodies were retrieved on Friday from the camp, which is a few hundred meters from Thailand's border with Malaysia, bringing the total to 26.

"From initial forensic investigation at the site there are no marks on the bones or breakages that would suggest a violent death," Police Colonel Triwit Sriprapa, deputy commander of Songkhla Provincial Police, told Reuters.

"It is likely that they died from disease and malnutrition."

The discovery of a camp hidden deep in the jungle in southern Thailand, a regional human trafficking hub, was a sharp reminder of the extent of human trafficking in the Southeast Asian country and comes as Thailand scrambles to improve its record in fighting the illegal trade.

Illegal migrants, many of them Rohingya Muslims from western Myanmar and Bangladesh, brave often perilous journeys by sea to escape religious and ethnic persecution and to seek jobs in Malaysia and Thailand.

Police are focusing their investigation on a human trafficking network linked to the camp, said Police Colonel Anuchon Chamat, deputy commander of Nakorn Si Thammarat Provincial Police.

"It is an ongoing investigation but we have reason to believe that one suspect arrested in Nakorn Si Thammarat and his associates was directly linked to this camp," Anuchon said.

Three survivors were found near the camp, including two aged 14 and 17. Police do not expect to find further bodies at the site, Triwit said.

"A witness said 30-40 people were brought to the camp at a time. The camp could have held up to 200 people," Triwit said.

The Thai government said on Saturday it was determined to rid the country of human trafficking. Prime Minister Prayuth Chan-ocha has acknowledged the complicity of some Thai authorities in smuggling people.

Last year, Thailand was downgraded to the U.S. State Department's lowest category - or Tier 3 - in its annual Trafficking in Persons Report, which assesses how governments around the world have performed in fighting human trafficking.

(Additional reporting by Panarat Thepgumpanat)