For now, makeshift embankments are preventing the oil from getting into Halda, Bangladesh’s largest fish spawning ground. But stopping the oil from polluting the river will be a huge challenge if the weather changes.

Three wagons fell into the canal on Monday. The Hathazari administration has been able to retrieve around 10,000 litres with the help of local until Tuesday morning, Upazila Nirbahi Officer (UNO) Md Ruhul Amin said.

Prof Dr Manzoorul Kibria of Chittagong University, who is also a Halda researcher, said the oil spread over a two-kilometre area of the canal.

Amin said they set up 10 makeshift embankments to stop the oil from spreading further. “We’re trying to prevent the oil from entering the river, which is about 10 kilometres from here,” he said.

Prof Kibria said Halda’s aquatic life and biodiversity might have suffered a huge blow if it were not for the embankments. “Halda has narrowly been saved from a disaster,” he said.

The Department of Environment, Hathazari municipality, and Chattogram Port Authority also joined the cleanup drive in Egaromile area. The railway authorities formed two committees to investigate the accident.

To encourage the locals to collect the spilled oil, the local administration said it will buy oil from them at Tk 20 per litre.

UNO Amin said the river is not free from danger yet. “Everything will be okay if it doesn’t rain,” he said. “The makeshift embankments, though weak, have been useful.”

Meanwhile, very severe cyclonic storm ‘Fani’ was centred about 1,270 km Southwest of Chattogram port, the Met Office said. It is likely to intensify further and move in a north/northwesterly direction.

Maritime ports of Chattogram, Cox’s Bazar, Mongla and Payra have been advised to keep hoisted distant warning signal number 2.