Four Thai nationals were charged in a Malaysian court on Friday with trafficking migrants from Myanmar, in connection with the discovery of mass graves near the Thai-Malaysian border in 2015.

They were charged a day after they were extradited by Thai authorities in what Thailand’s deputy national police chief, Pol Lt Gen Surachate Hakparn, described as a demonstration of the country’s commitment to cracking down on human trafficking.

The Thais were charged in a case related to the 2015 discovery of more than 100 graves of Rohingya and Bangladeshi human smuggling victims near Malaysia’s border with Thailand.

Berna News reported that, if found guilty, the suspects face a maximum of 15 years in jail and a fine, or both.

It said the four, who were not represented by lawyers, were charged under Malaysia’s anti-trafficking and anti-smuggling of migrants laws.

The accused nodded in understanding when the charges were read out in Thai by a court interpreter before Judge Musyiri Peet, at the Sessions Court in the northern state of Perlis, according to Berna News.

The next court date is set for July 25th, Musyiri said.

According to the charge sheet, the four suspects are “Kaeofainok”, 30, Jepha Lapi-E, 51, Somphon A-dam, 51, and Amree Nesalaeh, 58.

Arun, Jepha and Somphon trafficked a Myanmar national, Mohd Belal, between August and March 2014 at Wang Kelian in Padang Besar, a district in Perlis.

The fourth accused, Amree, allegedly trafficked another Myanmar national, Zedul Islam, between February and April 2013 at the same location.