Wild elephants trampled sleeping Rohingya refugees in Bangladesh in the early hours of Saturday, killing three children and a woman in the second such incident since the arrival of hundreds of thousands of refugees from Myanmar in just a few weeks.

Many trees on the forested hills of Balukhali in southern Bangladesh, where the incident took place, have been chopped down to house the massive influx of Rohingya Muslims escaping violence in neighbouring Myanmar.

Tarpaulin and bamboo shelters have been built on elephant walkways in some areas, sparking environmental concerns, as the country struggles to accommodate an unprecedented number of people.

Besides those killed, four refugees from neighbouring tents were injured and were in critical condition at Sadar Hospital in Cox’s Bazar, the town’s additional superintendent of police Afrujul Hoque Totul told Reuters.

At the refugee camp, cooking utensils the family had brought from Myanmar lay crushed under a jumble of bamboo sticks and clothes.

Abdul Sukoor, 30, whose tent on the edge of the camp was also trampled, said he and his family managed to escape when they heard the screams of other refugees as the elephants approached.

He is now moving to a tent further inside the camp, but said he was still worried. “We have to be constantly alert at night,” he said.

More than 530,000 refugees from Myanmar have fled to Bangladesh over the last two months since attacks by Rohingya militants on security posts triggered a Myanmar army operation that the United Nations has described as ethnic cleansing.