A mine belonging to Brazilian petrochemical giant Braskem ruptured and partially collapsed on Sunday in the northeastern coastal city of Maceio, the city’s civil defence authority said.

Video the authority distributed shows a sudden bubbling of the water in the Mundau lagoon in the city’s Mutange neighbourhood, caused by the mine’s rupture.

The area had previously been evacuated and there were was no risk to any people, it said in a statement.

Braskem’s 40 years of rock salt mining in Maceio has prompted the displacement of tens of thousands of people and on November 28 the company alerted authorities of the imminent risk the mine would collapse. Land around the mine has been steadily sinking ever since, falling a total of 2.35 metres as of Sunday morning.

On November 30, Alagoas state governor Paulo Dantas warned of the possible “formation of large craters” following the mine’s collapse and said federal teams would arrive that night as back up.

Local residents were told not to travel near the area.

In the first few days, Braskem sent regular updates, including possible times at which the mine could collapse.

Between 1979 and 2019, when Braskem announced the shutdown of its rock salt operations in Maceio, the company operated 35 mines.

Troubles in Maceio began a year earlier, when large cracks first appeared on the surface. Some stretched several hundred metres. The first order to evacuate some areas — including parts of the Mutange neighborhood — came in 2019.

Since then, residents in five neighbourhoods have accepted Braskem’s payouts to relocate. According to the Brazilian Senate’s website, some 200,000 people in Maceio were affected by the company’s mining activities.

In July, the company reached a 356 million dollar (£284 million) settlement with the coastal city.

Aside from mine 18, which ruptured on Sunday, Braskem says it is in the process of filling eight other cavities with sand.

Rock salt mining is a process of extracting salt from deep underground deposits. Once the salt has been extracted, the cavities left behind can collapse, causing the soil above to settle. Structures built on top of such areas can topple.

Braskem is one of the biggest petrochemical companies in the Americas, owned primarily by Brazilian state-run oil company Petrobras and construction giant Novonor, formerly known as Odebrecht.