A huge wall of red sludge descended on the south-eastern village of Bento Rodrigues when two dams holding waste water from an iron ore mine collapsed.
Hundreds of rescue workers continue to search for 26 people who are missing feared dead.
The authorities have confirmed the death of one person.
Two other bodies have been retrieved, but officials are not sure whether their deaths were connected to the breach of the dams on Thursday afternoon.
They will carry out DNA tests to check if they are related to the 13 mine workers and 13 residents, including five children, who are missing.
"It is unlikely that the 13 workers who were at the dams will be found alive. We have to accept that," said Mr Pimentel.
Two men, who are related, were located on Sunday evening at a nearby hotel, bringing the number of people feared dead from 28 to 26.
Their family was not aware of their whereabouts and had reported them as missing.
Residents complained of not being warned once the Fundao and Santarem dams collapsed.
Many saved their lives by running to higher ground when they heard the noise of the approaching sludge.
The mine is owned by Vale and BHP Billiton and is operated by Samarco.
Samarco head Ricardo Vescovi told the AFP news agency that to the best of his knowledge, Brazilian law does not require an emergency alarm for dam failures.
The authorities approved the company's emergency response plan, he said.
The authorities say there is no risk of a third dam in the area collapsing.
The thick red mud surge engulfed cars and lorries, and destroyed homes shortly after the dams collapsed.
The floodwaters and mud have reached towns up to 70km (40 miles) away.
There are fears that the iron ore residue in the mud poses a health risk.
More than 500 people lived in Bento Rodrigues, which lies about 7km (four miles) south of the burst dams.
It is part of Mariana, an old colonial town and a major tourist attraction in Brazil.
Mine owners Samarco do not have information on the environmental impact of the dam bursts, a spokesman told the Reuters news agency.
The cause of the breach is not yet known.
The authorities are investigating whether low-intensity tremors registered in the area on Thursday could have played a part in the tragedy.
Hopes of finding survivors of mudslides and floods on Thursday in Brazil are fading, Governor Fernando Pimentel of Minas Gerais state has said.