The Ministry of Shipping and the Forest Department have constituted two committees to probe the spill of more than 350,000 litres of furnace oil in the Sundarbans, a UNESCO World Heritage site.
MS Harun & Co, the owner of the capsized oil tanker, 'OT Southern Star 7’, has begun salvage operations with the help of three private rescue vessels.
Two of the ships have towed away the damaged vessel to prevent it from sinking fully.
Two ships of the Navy and the Bangladesh Inland Water Transport Authority (BIWTA) have started for the spot.
The damaged tanker remained in the same position since Monday with its fore submerged and aft above water.
Coast Guard personnel conducting the salvage operation said they could not trace the cargo ship’s Master Mokhlesur Rahman until Wednesday morning.
'OT Southern Star 7' was on its way to a power plant in Gopalganj from the Khulna Padma Oil Depot, carrying 357,664 litres of furnace oil.
After setting off on Monday afternoon, it anchored on the Shela River at the forest's Chandpai Range for the night.
The taker was hit from behind by another empty cargo ship 'Total' around 5am Tuesday amid dense fog, Mongla Coast Guard's Contingent Commander (West Zone) Captain Mehedi Masud said earlier.
MS Harun & Co Manager Md Giasuddin said seven crew members of the tanker swam to the shore but Master Rahman could not.
After surveying a 20 sq km area inside the forest, Assistant Forest Conservator Abul Kalam Azad said he thought all of the 357,664 litres of furnace oil from the tanker had spilled.
This correspondent found stains of oil on trees on the banks of the Shela during a visit on boat from Monga to Joymoni pier on Wednesday morning during low tides.
Forest Department officials said an oil slick had spread to Andharmanik, Nandabala, Joymoni and Harintana areas through the canals linked to the Shela River.
Oil slick was seen also in the Rupsha River.
Shipping Minister Shajahan Khan told reporters on Wednesday that two BIWTA salvage ships -- Pratyaya and Nirvik -- had started for the spot from Narayanganj and Barisal respectively.
He said tugboat Kandari-10 was on its way to Bagerhat from Chittagong.
The minister said powdered chemicals would be sprayed from Kandari-10 so that the oil on the water subsided and risk of reduction of oxygen in the water declined.
Commander Monir Mallick of Bangladesh Navy's Khulna region said that two of their ships -- Shah Paran and Akteruddin -- started for the spot from Mongla and Hiron Point respectively with 16 divers on board.
He said they would try to use ancient method of using bamboos and banana trees to remove the oil from the water surface.
Minister Khan said the authorities had identified ‘Total' which hit the tanker.
He said ‘stern actions’ would be taken against owners of the vessel.
Assistant Forest Conservator Abul Kalam Azad filed a Tk 1 billion compensation suit against owners of ‘Total’ and Southern Star 7 over the incident.
The Forest Department constituted a three-member committee headed by Assistant Conservator of Chandpai Range at Sundarban's West Zone Belayet Hossain to probe the accident.
The other members of the committee are Chandpai Station’s Abul Kalam Azad and Dhangmari Station’s Prahlad Chandra.
Shipping Department’s Nautical Surveyor and Examiner Captain Giasuddin Ahmed is leading the shipping ministry-formed probe committee. The three-member committee also includes Shipping Department Special Officer (Marine Safety) Golam Mainuddin Hassan and an executive magistrate.
The shipping ministry-formed committee has been asked to find out the cause of the accident, determine the loss, identify those responsible for it and make suggestions to prevent its recurrence.
Forest Department officials said the situation was getting worse as the local government offices, including the Forest Department and Mongla Port Authority, had no tools to control or clean up the oil spilled.
Sundarbans east region Divisional Forest Department official Amir Hussain Chowdhury told bdnews24.com: "The Mrigmari-Nandabala-Andharmanik dolphin sanctuary is facing serious threat due to the oil spill. The sanctuary may have to be moved."
The Sundarbans is the biggest roaming ground for Irabati Dolphins locally known as Sushuk. The area adjacent to the Shela River has been declared dolphin sanctuary by the government.
Biodiversity and ecology researcher Pavel Partha told bdnews24.com: "The oil will reduce the amount of oxygen in the water. This will create a crisis for all the aquatic creatures including the dolphins."
He was concerned that the plants and aquatic resources of the mangrove forest would be fatally harmed.
His concerns were echoed by professor of Khulna University's environmental science department Dilip Kumar Dutta.
"This huge amount of oil on the water would heavily affect the coastal biodiversity for a long time," he said.
He said there was a slim chance that high and low tides would fast clean up the oil from that part of the river because water flow in the downstream was not strong.
The Ghashiakhali channel, used as India-Bangladesh water protocol route and maritime communication route for the country's southern region, was closed nearly three years ago after Mongla's Nala River and Rampal's Kumar River filled up.
Since then BIWTA has been using Shela River inside the Sundarbans as an alternative route.
Environmentalists had demanded closure of the waterway on several occasions over the years as it had a great risk of ecological disasters.
On Sept 30, a cargo vessel carrying raw materials for a cement factory capsized at Mongla Port's Pashur Channel.
Only 18 days earlier, another vessel carrying similar materials went down at Harhbarhia in the same channel.
Both ships are yet to be salvaged.
Minister Khan said the channel should be closed to protect the biodiversity of the Sundarbans.