By Mauricio Weibel and Juan Garff

SANTIAGO, Chile — Most of the fires that have devastated the central Chilean port city of Valparaiso and killed 15 people have been contained, the head of the government’s forestry agency said.

Substantial gains have been made against the blazes that broke out at the weekend but firebreaks must be established to prevent the spread of the flames to housing and dry vegetation if winds pick up, Aaron Cavieres, the executive director of the National Forest Corp, said late Monday.

“We have a breakthrough in the containment of the fire, but we cannot declare it controlled,” he said.

Hopes were also raised by the weather forecast, which predicted winds to die down Wednesday.

But Cavieres’ agency warned that it could take firefighters until the beginning of May to fully extinguish the blazes.

Interior Minister Rodrigo Penailillo said the death toll could rise further.

Dry conditions and high winds caused the original fire, which broke out Saturday, to flare into numerous blazes across the hills of the city known as “The Jewel of the Pacific.”

More than 11,000 people have been left homeless, about 2,500 apartments have been destroyed and 2,800 acres have burned, Penailillo said.

The historic city center, which is a World Heritage Site, has so far been spared.

What caused the fires to break out remained unknown.

President Michelle Bachelet vowed to rebuild the city of 270,000 people after fires “of never-before-seen dimensions.”

“I want to express my full solidarity and that of the government with the people and families who are being affected,” Bachelet said a month after taking office.

About 1,250 firefighters are battling the blazes with the help of 30 aircraft, including six from neighboring Argentina, and 3,000 soldiers and police who are providing security in the ravaged city, known for the brightly painted houses and funicular elevators on its hillsides.

Trucks of food, clothing and other aid are pouring into the port, 75 miles northwest of Santiago, from other parts of Chile.

Guillermo de la Maza, head of the National Office of Emergency, said he suspected arson to be the cause of the blazes, but Penailillo ruled that out. Police said they suspected two vultures that landed on high-voltage electrical lines to be the culprits, a theory prosecutor Eduardo Fernandez nixed.

Investigators, meanwhile, were looking into whether accelerants had a part to play in the blazes.