Brazilian federal prosecutors announced homicide charges Thursday against 21 people, including senior mining executives, allegedly responsible for the deadly collapse of the Samarco iron-ore mine dam last year.

The lead prosecutor in the case, Jose Leite Sampaio, made the announcement in a televised news conference in Belo Horizonte, near Mariana, the site of the disaster, where on November 5, 2015, the failed dam unleashed a torrent of muddy water down the River Doce, killing 19 people.

It was branded Brazil's worst environmental disaster, drawing comparisons with the 2010 Deepwater Horizon oil rig explosion which killed 11 workers and triggered a devastating spill in the Gulf of Mexico.

In a statement, prosecutors denounced the mining companies for reckless policies in pursuit of greater profits that amounted to "qualified homicide," which in Brazilian law is more serious than ordinary manslaughter.

"Security was always of secondary importance. The increase in production at Samarco sought to compensate for the falling value of the ore in order not only to maintain but also to boost profits and dividends," Sampaio said. "It should have taken steps to promote the safety of the dam."

Prosecutors said Samarco -- which operated the mine and is owned 50-50 by Brazil's Vale and Anglo-Australian giant BHP Billiton -- ignored basic responsibilities.

They accused the mining companies of not taking into account the fate of communities downstream or even their own employees, saying there were not even "sirens or warning lights" in case of disaster.

The accused included the chief executive of Samarco at the time of the tragedy, Ricardo Vescovi, as well as operations managing director Kleber Terra, and three operations managers.

They could face sentences of "up to 54 years," prosecutors said in the statement.

The three companies themselves also face charges for a total of 12 different environmental crimes, prosecutors said.

- Vehement rejection -

Vale said in a statement that it "vehemently rejects the charges presented by the federal prosecutor's office."

BHP also issued a statement, saying it "rejects outright the charges against the company and the affected individuals. We will defend the charges against the company, and fully support each of the affected individuals in their defense."

The charges still need to be approved by a judge before a jury trial would start.

The breaking of the tailings dam unleashed a massive flood of sludge into the River Doce, reaching the Atlantic Ocean.

Drinking water supplies were cut for hundreds of thousands of people, a village was flattened, and local fishing and tourist businesses were badly impacted. According to prosecutors, 14 tons of dead fish were collected in the aftermath.

The mining companies have agreed to pay billions of dollars in compensation but in May prosecutors filed a civil lawsuit against Vale, BHP and Samarco seeking 155 billion reais ($49 billion).