A landslide killed at least 18 people, including children, as they slept in their tents at an unlicensed campsite in Malaysia on Friday, officials said, as search teams scoured thick mud and downed trees for survivors.

The landslide in Selangor state bordering the capital, Kuala Lumpur, occurred before 5:00pm GMT, tearing down a hillside into an organic farm that officials said was operating the campsite illegally.

Among the victims were three children and 10 women, according to the fire and rescue department.

Camper Teh Lynn Xuan, 22, said one of her brothers was killed and another was being treated in hospital.

“I heard a loud sound like thunder, but it was the rocks falling,” she told Malay-language daily Berita Harian.

“We felt the tents becoming unstable and soil was falling around us. Luckily, I was able to leave the tent and go to some place safer. My mother and I managed to crawl out and save ourselves.”

The disaster struck about 50 km north of Kuala Lumpur in Batang Kali, just outside the popular hilltop area of Genting Highlands, known for its resorts, waterfalls and natural beauty.

The earth fell from an estimated height of 30 metres and covered an area of about an acre (0.4 hectares), according to the fire and rescue department’s state director.

An initial investigation showed an embankment of about 450,000 cubic metres of earth had collapsed, according to minister of natural resources, environment and climate change, Nik Nazmi Nik Ahmad.

There were 94 people caught in the landslide but 61 were safe, with 15 missing, according to the Malaysia National Disaster Management Agency.

Eight people were hospitalised, including a pregnant woman, while others had injuries ranging from minor cuts to a suspected spinal injury, health minister Zaliha Mustafa said.

District police chief Suffian Abdullah said the dead were all Malaysians, including a child of about five. Close to 400 personnel were involved in the rescue mission, he said.

Pictures posted on the Father’s Organic Farm Facebook page show a farmhouse in a small valley, with a large area where tents can be set up. The farm owners did not immediately respond to a request for comment.