New Delhi, India (CNN) -- Ethnic clashes in India's northeastern Assam province have left 32 dead as of Wednesday and sent an estimated 150,000 fleeing their homes to escape the violence, police said.
Long-standing tensions between the predominant Bodo tribes people and minority migrant Muslim settlers erupted into bloodshed nearly a week ago and has largely gripped the province's Kokrajhar district, which borders on neighboring Bhutan to India's north, said Assam police chief J.N. Chaudhury.
What sparked the mayhem is not yet known and under investigation, he said. But it has resulted in incidences of attacks and counter attacks between the two groups, CNN sister network CNN-IBN has reported.
Five of those killed died when police fired on mobs engaging in rioting and arson, according to Chaudhury, who said that the district had witnessed similar fighting in the 1990s and the early 2000s.
"For now, our priority is to stop the violence and arson. It may take some days to rebuild trust," he said.
Peace committees were set up between tribal and migrant communities when clashes erupted in the past, Chaudhury said.
Angry mobs disrupted rail service by attacking train cars with bricks and sitting on tracks, bringing service to a standstill. R.S. Virdi, general manager of Northeast Frontier Railway, told CNN that 34 trains were held up at various stations.
"We are not originating any new trains until we have clearance from the state authorities," he said, adding that train service was being gradually restored as security personnel moved in.
The Assam region, known around the world for its tea production, is also a major petroleum supplier, but the region has remained particularly poor.
India is known for its diverse mixture of cultures, religions and ethnic backgrounds, which at times has led to conflict between groups.
Assam has a high concentration of extremist groups of varying backgrounds, reflecting a checkerboard of ethnic and political interests. But police have not blamed any insurgent group in this week's violence, citing instead rioting mobs.
Harmeet Shah Singh reported from New Delhi and Ben Brumfield, from Atlanta. CNN's Sumit Galhotra contributed to this report.