As clean-up efforts after an oil spill in Bangladesh's Sundarbans region begin, some online are criticising what they see as the government's slow response. 

A tanker carrying an estimated 350,000 litres of oil sank on Tuesday after colliding with another vessel in the Sundarbans' Shela river. On Thursday, officials said the damage had already been done to the river and joining canals. The area is home to rare river dolphins and other wildlife. 

Bangladeshi fishermen began cleaning up the site with sponges and sacks. The government has also sent a ship with dispersants to the area, though environmentalists warn these chemicals could harm the ecosystem.

The Sundarbans' chief forest official said authorities were unsure of how to initially respond to the spill. Some online criticised what they called a slow response from the government: