Authorities said the fire in the mountainous region, which killed many people in their cars as they tried to escape, was 85 percent under control after more than 1000 firefighters worked overnight.
Data from the European Forest Fire Information System showed that an area of more than 30,000 hectares had been affected, making it the largest ever fire in Portugal.
The accident was initially reported by the Civil Protection Agency, which is overseeing firefighting operations.
The CPA said that an abandoned caravan containing gas bottles had exploded in the area, and may have misled people into thinking there was a crash.
Questions also remain over how so many people could have died, a lot of them perishing on a single road that locals say should have been sealed off by first responders.
A spokesman for Portugal's Civil Protection Agency also said he couldn't confirm a crash.
He said he believed the fire had been deliberately started, and called for a "scientifically based study" to try to establish the truth.
"This is great progress", Vitor Vaz Pinto told journalists, according to AFP news agency.
Galileo and Highland Real Star at Royal Ascot
Trainer Jean-Claude Rouget said of his 5-2 favourite: "I hope now she's in a good place for the rest of the season". And so it proved once again as Ryan Moore's companion bravely fended off all-comers to score at odds of 9-4.
More than 1,500 firefighters along with water-dropping aircraft are working to douse the flames.
A Reuters photographer in the area said he saw a plane fly out of view and shortly afterwards he heard an explosion.
More than 1,000 firefighters and nine water-dropping aircraft are battling the blaze in Pedrogao Grande, which is raging for a third consecutive day.
Secretary of State for the Interior Jorge Gomes said the wildfires were gradually ebbing and being contained.
The blaze appeared to have been brought under control on Tuesday, only for it to suddenly flare again, forcing authorities to evacuate 40 hamlets near the village of Gois.
Temperatures forecast to reach 43 degrees Celsius (109 Fahrenheit), gusting winds and bone-dry woodland were fueling the blazes, Vaz Pinto said.
Costa's order asked three questions: whether the extreme weather could explain the scale of the disaster, why emergency services communications at times didn't work, and why the road where the deaths occurred was not closed.
Comments