KUALA LUMPUR, Oct 18 — Last year’s landslide near Batang Kali that killed dozens of campers including children was "likely” caused by "natural failure”, the Natural Disaster Management Agency (Nadma) said in its investigation report of one of the deadliest disasters in the country.

It said human activities could have also played a role, but no concrete proof was found to support the theory. Environmentalists had previously called for scrutiny of development around the hilly area, which they believed could have caused the slopes to collapse.

"Without substantial evidence linking specific human activities to the landslide, it is reasonable to consider it as primarily a result of natural failure,” the agency said as part of the summary of its investigation report released today.

In December 2022, 31 people were killed in the landslide that struck at 2.42am after almost five days of heavy rain — 13 of them children. Most of the victims, 91 in total, were asleep in tents on a popular camping site that belonged to owners of a commercial orchard. The search and rescue team managed to save 61 survivors.

Natural Resources, Environment and Climate Change Minister Nik Nazmi Nik Ahmad said the disaster was likely caused by the embankment failure at an area of 500 metres (m) in length, 200 m wide and a depth of 8m, moving approximately 450,000 square metres (sq m) of soil.

Environmentalists immediately pointed to overt development as the potential cause, prompting family members of victims to call for an investigation.

But Nadma said it found no significant anthropocenic causes even if human activities could have had some impact. It also found routine slope and road maintenance in the area where the land had collapsed was done as scheduled just before the landslide occurred.

The investigation was carried out by the Landslide Working Committee, consisting of various experts.

During incident, the committee said two major slope failures had occurred with the first occurring after the slope’s structure experienced high water saturation which led to a collapse zone with an average depth of 14m and 120m in length.

"The first landslide took place at approximately 2am with a dimension of slope failure of 120m length and a maximum depth of 14m. Due to the soil conditions, the debris reached the Riverside campsite located approximately 550m away," Nadma said in its executive summary of the investigation report made public this morning.

"Subsequently, the debris consisting of soil, rocks and trees from the first landslide mass accumulated at the toe of the failed slope, forming an artificial temporary dam...the failure mode is a combination of the rotational slide and debris flow," it added.

"Two significant factors that contribute to such events are rainfall and hydrogeology, which are related to the change in the underground water regime."