"The priority now is to save those people who could still be in danger".
About 700 firefighters worked to put out the fire, which broke out Saturday.
Interior Ministry official Jorge Gomes said Sunday that at least 30 people died inside their cars as they tried to flee. He says 17 others died right outside their cars or by the road, 11 people died in the forest and two people died in a vehicle accident related to the fire and information was missing on the other deaths.
No information was immediately given on how the others were killed.
"It is a time of pain but also. a time to carry on the fight" against the flames, President Marcelo Rebelo de Sousa told the nation in a televised address Sunday evening after the government declared three days of national mourning.
Officials describe as the "greatest wildfire tragedy of recent years". "Sad to learn of tragic loss of lives in the forest fire in Portugal".
The blaze on Saturday hit the mountainous area of Pedrogao Grande amid an intense heat wave and rainless thunderstorms.
Hundreds of firefighters were still battling the flames on Sunday.
At least 54 people were injured in the fire.
Pope Francis has led thousands of people in a moment of silent prayer for the victims of the Portugal fire. Earlier in the day, the Portuguese media reported about the total of 43 victims. In addition, a moment of silence for the victims of the blaze is expected at the Confed Cup football match between Portugal and Mexico.
"We express our condolences to those that have lost loved ones", the European Commission, executive arm of the European Union, said in a statement Sunday. Spain and France are both sending several firefighting aircraft.
Forest fires are common in the the Iberian peninsula during the summer months, but today's example is particularly extreme.
Deadly wildfires have swept through central Portugal, killing dozens in what the country's prime minister called the "biggest tragedy" in years. "We have provided support to a number of British people caught up in the incident and stand ready to support any others who may be affected".
Portuguese Prime Minister Antonio Costa said that Spanish rescuers would assist in efforts to control the blazes.
In 1966, a blaze in the forest of Sintra, west of Lisbon killed 25 soldiers trying to battle the flames. "The flames passed within two or three kilometres of my house", said local resident Isabel Ferreira, 62.