(Reuters) - A Vale SA VALE3.SA dam in Brazil that burst, killing at least 10 people and leaving hundreds missing, showed no structural flaws when it was inspected last September, the German firm that carried out the inspection said on Saturday.

FILE PHOTO: A rescue worker is seen after a dam, owned by Brazilian miner Vale SA, burst in Brumadinho, Brazil January 26, 2019. REUTERS/Washington Alves/File Photo

The death toll from the tailings dams rupture on Friday at Vale’s Corrego do Feijao iron ore mine in Minas Gerais state is expected to rise sharply, with more than 300 still missing in the country’s worst mining disaster since 2015.

German-based TUV SUD said on Saturday it had inspected the tailings dam last September and found it to be operating well.

“Based on our current state of knowledge, no damages were found,” a company spokesman said. “We will fully support the investigation and make available all documents required by the investigating authorities.”

The company declined to comment further.

TUV SUD is part of the TUV family of companies, which carries out a range of industrial inspections including of pipelines, tailings dams and even breast implants. However, each TUV entity has a complicated ownership structure among various parties.

In 2010, TUV SUD was suspended by a United Nations climate change committee for not following procedures and for giving “a positive validation opinion to some projects even though it had concerns.”

The cause of Corrego do Feijao dam rupture near the town of Brumadinho is not known. Vale Chief Executive Fabio Schvartsman said the dam was being decommissioned and equipment had shown it was stable on Jan. 10.

Tailings are the liquid or solid detritus left over from the mining process. Gold, copper, iron ore and other minerals are separated from base rock elements after they are removed from the earth.

That goopy mixture of leftover tailings is often toxic and is stored in nearby reservoirs held in place by earthen dams that are built higher the longer a mine operates.

But those tailing dams, some of which are among the largest structures in the world, are susceptible to erosion.

Brazil’s National Mining Agency has already ordered Vale to halt operations at the Corrego do Feijao site and state prosecutors have entered a motion to freeze 5 billion reais ($1.33 billion) in Vale’s accounts for damages.