As worries grow over the hundreds of dead fish found floating in Sungai Tonggak, near Gebeng in Pahang where bauxite mining had become a major cause of concern, the Fisheries Department says it is "nothing unusual".

This comes after several tests were conducted by state fisheries officers on water samples taken from the river, Pahang Fisheries Department director Adnan Hussain said.

"After some tests by our officers, the results showed that the incident was nothing unusual," Adnan is quoted by New Straits Times as saying last night.

"Initial tests showed the (cause of) dead fish had nothing to do with silt and mud. No other rivers here are affected except for Sungai Tonggak," he said.

A detailed report on the incident is expected to be completed in a week, Adnan added.

Kuantan residents are deeply troubled by "red sea" phenomenon at Balok beach.

They were especially alarmed when hundreds of dead mullets were washed up on the bank yesterday morning.

It was reported that there are no bauxite stockpiles near the river banks.

Balok Makmur Rukun Tetangga chairperson Abdul Rahman Ali, 57, has urged the authorities to conduct thorough tests to identify if the fish in the river is safe for consumption as the villagers sometimes catch fish from there.

Ab Razak Musa, 56, a resident from Taman Seberang Balok, said a similar incident occurred before, but there were fewer dead fish compared to now.

"With the bauxite issue a hot topic, we cannot rule out any possibility that river contamination from bauxite has killed the fish," Razak is quoted as saying.