More than 600 people have died after mudslides buried neighbourhoods in and around Teresópolis

A break in near-constant rain allowed rescue helicopters to deliver desperately needed food and water to some of the neighbourhoods in Teresópolis buried under the mudslides which have killed more than 600 people.

Rain clouds lifted, allowing about a dozen helicopters to manouvre through the mountains about 40 miles (65 km) north of Rio de Janeiro.

"The priority is the rescue of people who are still isolated. We have to take advantage of this break in the weather to help people in these remote, collapsed areas," said Alexandre Aragon, head of the Brazilian National Security Force.

The helicopters are not yet being used to evacuate people from areas still at risk of further mudslides should rains return. Instead, they were focusing on getting supplies to as many isolated areas as possible to keep people there alive.

The disaster struck in the early hours on Wednesday, when days of heavy rains unleashed tonnes of earth, rock and torrents of water down steep mountainsides and directly into towns over an area of about 900 sq miles (2,330 sq km). The known death toll stood at 626 people. Officials fear it will rise sharply as emergency workers reach the remote areas and find more bodies.

Anderson Correia de Oliveira, the local police commander, said that after four days, there would be no further "miracle" rescues of people buried under the mud.

There is no hope of finding anybody alive, he said. "It's not like an earthquake – people trapped under things have been drowned. There are no air pockets."

Desperate survivors have complained of receiving little or no help and Brazil's government at all levels has come in for criticism for the lack of urgency in helping the victims.

But Oliveira and other officials said that reaching the most remote and desperate areas was impossible by helicopter until today. The disaster area is full of steep mountains with jagged peaks, making navigation challenging even in good weather, he said. With clouds that hovered well below the mountaintops for days, helicopters could not be used.

That has meant people have simply had to save themselves, mostly by hiking miles from their neighbourhoods down to the centre of Teresópolis to fetch supplies.

President Dilma Rousseff designated $60m in aid for the state of Rio de Janeiro and the hardest-hit towns. The minister of national integration, Fernando Bezerra, said half the money would be in state and municipal accounts by Monday – six days after the disaster struck.

Rio state's civil defence department said 268 people were killed in Teresópolis and 283 in Nova Friburgo, a 45-mile drive to the west. Fifty-six died in neighbouring Petrópolis and 19 in the town of Sumidouro.