Two people were found dead after up to 50 people were engulfed in a landslide that hit a coastal motorway in the Brazilian state of Parana on Wednesday.
Six people have been rescued alive since the landslide, state officials said.
Officials said it was impossible to say how many passengers were travelling in the 16 vehicles known to have been hit by the landslide and the number of victims could differ from the estimate.
"It's hard to know the exact number of victims. A vehicle could have one to five people inside. We're working with an estimate of 30 to 50 people missing," said emergency response chief Manoel Vasco.
The landslide hit the BR-376 motorway in the city of Guaratuba after intense and continuous rain in the region.
Aerial images released by the emergency services showed a massive smear of mud that swept away everything in its path ― including a chunk of motorway and the vehicles on it.
Rescue workers said the bad weather and remote location were complicating the search effort.
They are using drones with heat-detecting cameras in the hope of finding survivors.
"Fifty-four firefighters have been working non-stop for more than 35 hours," the Parana state security authority said in a statement on Wednesday, noting also the concern over further landslides.
Among the six survivors was Guaratuba mayor Roberto Justus.
In a video on social media, Mr Justus said he was “alive by the grace of God”, AFP news agency reported.
“It was horrible,” he said. “The mountain just fell on top of us. It swept away every last car.”
“The teams are working around the clock,” Mr Vasco said. “The situation in the area, which is already at risk, is likely to get worse in the coming days if it continues like this.”
Mr Vasco said rescuers had to tread carefully, because more landslides could happen, especially as the rain is expected to get worse. The motorway lane is also at risk of giving way due to the weight of the debris.
The BR-277 road to Paranagua and Antonina ports has been closed to traffic towards the coast since Tuesday.
About 80 per cent of goods exported from Paranagua, Brazil's second-biggest port for grain and sugar, arrive by lorries, the port authority said, declining to estimate losses from the disruption.
Brazil is frequently hit by deadly landslides.
The national weather service Inmet has issued heavy rain warnings for several states.
At least one other person died on Wednesday after a section of road was washed out, sweeping away the victim's car, in the north-eastern state of Segipe, Brazilian media reported.
In February, more than 200 people were killed in a series of landslides in the picturesque south-east tourist town of Petropolis.
In April, torrential downpours triggered flash floods and landslides across Brazil's Rio de Janeiro state, killing at least 14 people including eight children and leaving five missing.