Two other people have been seriously hurt by the fires, which have destroyed 37 homes and a boutique hotel as they advanced on the Madeiran capital, Funchal, regional government president Miguel Albuquerque told a press conference.
A man is being held on suspicion of lighting three fires in the Sao Roque neighborhood of northern Funchal, he said, while three others have been arrested for trying to light additional fires while the main blazes were being fought.
Fanned by unpredictable, high winds on the mountainous island amid unusually hot, dry weather, the blazes have created apocalyptic scenes, disrupted flights and left residents fearful for their homes.
Aurelien Dutrievoz, who lives in a neighborhood in east Funchal, filmed nervously as huge plumes of smoke billowed over residential areas from fires he estimated were about 5-8 kilometers (3-5 miles) from his home.
"The fire is spreading quickly cause of several factors: strong wind, high temperature (35˚C), and gas explosions from the houses which are burning," Dutrievoz said in an email to CNN.
More than 300 people have sustained injuries in the fires, most due to smoke inhalation or minor burns, Albuquerque said. One of the seriously injured patients has been flown to the Portuguese capital, Lisbon, for treatment. Eighty people remain hospitalized, he said.
Fred Schlegel and his family checked into the Choupana Hills Resort & Spa at the popular tourist destination from their home in Leberge, France, near Toulouse, on Monday, about the time the wildfires began that day.
By Tuesday, authorities had evacuated the hotel. He noted that winds had whipped up the fire, and black smoke at times made roads impassable.
By Wednesday, after a rough night, they checked into another hotel to continue the vacation they had planned for six months.
"The wind has almost completely stopped, the fire is pretty much constrained ... so we are relaxing again and enjoying Madeira :-)," he wrote.
In positive developments, Albuquerque said, the high temperatures and strong winds are forecast to drop.
Public servants have been given the day off to assist efforts to relocate people away from the fires. Two hospitals and two homes for the elderly have been evacuated, with 950 people sheltered in army barracks and others housed in schools around the island.
Dozens of reinforcement firefighters have been brought in from Lisbon and the Azores -- Portugal's other autonomous region -- to battle the blaze.
Portugal's President, Marcelo Rebelo de Sousa, is to visit Madeira Wednesday, while the Prime Minister, Antonio Costa, will visit affected municipalities tomorrow, the prime minister's office said in a statement.
The fires have raged as Madeira, a popular tourism destination more than 800 kilometers (about 500 miles) southwest of the Portuguese mainland, has been enduring a summer heatwave.
On mainland Portugal, more than 3,200 firefighters are currently battling more than 100 fires that have been raging amid the arid summer heat, causing chaos across the country, according to the Portuguese National Authority of Civil Protection.