Several villagers claim the stench is overpowering and caused them to suffer dizzy spells.

Kampung Melayu Pandan Residents’ Association chairman Fauzi Mohamad, 51, said the foul smell was noticed around 7.30am today.

“I saw the river water had receded, but the colour is something I have never seen in my life – black, murky and oily.

“The stench is overpowering; anyone who breathes it in for a while will feel their throat go dry,” he said when met in the village.

Meanwhile, Mizal Abdul Hashim, 42, a supervisor at a kindergarten in the village, said the preschool was closed as a safety measure.

“The kindergarten is right beside the river, and the smell lingers in the classroom, so we decided to take precautionary measures and closed,” he said.

Resident Mohammad Jaafar, 66, also reported smelling the same odour around his home at midnight, which caused him a headache. The stench subsided a little after a few hours, he added.

A survey of the affected areas indicated a sharp gas-like odour that caused headaches if one remained in the area for too long.

Tebrau fire and rescue station operations commander Khairul Azhar Abd Aziz said 19 personnel, including from the Larkin fire and rescue station, inspected the area as soon as they received a report at 1.30am today.

State health and environment committee chairman Ling Tian Soon said an initial analysis of water and soil samples from Sungai Pandan taken by the Johor fire and rescue department revealed the presence of yet-to-be-identified chemical substances.