A rupture at a rock salt mine in north-eastern Brazil has heightened fears of an impending total collapse.
Video recorded by the civil defence authority showed murky water bubbling up in the Mundaú lagoon near the city of Maceió, where the mine is located.
The closed mine was operated by Brazilian petrochemical giant, Braskem.
Over the past four decades, tens of thousands of residents have been displaced due to the destruction caused by the extraction of rock salt.
The rupture, which caused water from the lagoon to enter the mine, happened at 13:15 local time (16:15GMT) on Sunday.
Braskem confirmed that cameras monitoring the surroundings of the mine, known as Mine 18, had detected “an unusual water movement” in the lagoon’s soil.
The mayor of Maceió, João Henrique Caldas, flew over the lagoon in a helicopter to inspect the damage.
He said the rupture – which according to him affected an area measuring 60m (200ft) in diameter – did not currently pose a threat to any people because those living nearby had already been evacuated.
He added that the mine was expected to stabilise.
However, residents of the city have expressed their concern at the speed at which the ground above the mine has been sinking.
Official measurements show that the ground subsided a total of 2.35m between 30 November and 10 December.
While Maceió’s office for civil defence warned on 29 November that Mine 18 was at imminent risk of collapse, the city’s problems with rock salt mining date back further.
In 2018, buildings and roads in five neighbourhoods began to crack. In the five years since then, more than 14,000 buildings have had to be evacuated, affecting around 60,000 people.
The abandoned neighbourhoods have turned into ghost towns.
The damage was originally blamed on heavy rains and seismic tremors. But a 2020 federal study found the cracks and the soil subsidence were caused by rock salt mining carried out by Braskem.
For decades, the Brazilian petrochemical company had operated dozens of mines in the region.
Rock salt, which is used as a raw material in the production of PVC, is extracted from deep underground deposits and the holes left behind can cause the soil above to sink.
Braskem disputed the findings of the study carried out by experts from the Brazilian Geological Service, saying they were flawed.
Nevertheless, the company closed its mines in Maceió in 2019 and earlier this year it reached a settlement with the city worth 1.7bn reias ($343m; £273m) for land subsidence and relocation damages.
Following warnings about Mine 18’s imminent collapse, the municipal authorities have asked to negotiate a new compensation agreement with the company to include “new damages”.
Source : BBC