RANAU, Sabah (THE STAR/ASIA NEWS NETWORK) - Rivers clogged with fallen trees and boulders following the earthquake in Sabah on June 5 is affecting Ranau district's water treatment plant.

Universiti Malaysia Sabah geologist Dr Felix Tongkul said the surge of mud, rocks, boulders and debris from Sungai Mesilau flowed into Sungai Liwagu.

As the surge headed downstream, it caused more trees to fall and the debris field increased, choking the water treatment plant's sluice gates, he said during a visit there on Wednesday.

Dr Tongkul said the choking of upstream Sungai Mesilau was expected as the magnitude 5.9 earthquake had loosened soil, rocks and boulders along the mountain slopes. Rainfall then caused the waters to surge and overflow the Sungai Liwagu reservoir.

He said clearing the 1km-long debris immediately at the reservoir was impossible but called on the authorities to ensure flow to the sluice gates.

"The fear is that if rain persists, more mud and rocks would be washed down, blocking the gaps where water is still flowing," he said.

He added that the situation would become dangerous if there was a total blockage.

Sporadic aftershocks have been felt almost daily in Sabah since the 6-magnitude quake, which left 18 people dead, including 10 from Singapore.