Police on Thursday were looking for four Uighurs refugees who escaped nearly three years of detention in Thailand’s northeast.

The four refugees, all men, escaped the immigration detention center in Mukdahan province Tuesday night. Police believe they’re still in the province, likely begging for food, according to Col. Komen Suphap, provincial immigration chief.

The three other male Uighurs, all held there since June 2016, escaped with them but have since been re-arrested.

Uighurs fleeing their homes in western China often pass through Thailand, where they are regarded as illegal immigrants and subject to detention. China has engaged in widespread persecution of the Muslim-majority ethnic group in Xinjiang province, placing an estimated one million Uighurs in political labor camps.

In July 2015, Thailand deported more than 100 Uighurs against their will back to China under pressure from Beijing.