MADRID — Thousands in the central Spanish town of Sesena were allowed to return home Saturday as firefighters tamped down a massive tire fire that had coated the area in thick, toxic smoke.

The regional government of Castilla-La Mancha lowered the danger level Saturday and permitted residents to return with the recommendation that windows should be kept shut and surgical face masks be used when outdoors.

It had ordered the evacuation of up to 9,000 people Friday from a large apartment block complex as plumes of acrid black smoke rose from the dump, which Spanish media says contains an estimated 110,000 tons of used tires.

Regional spokesman Francisco Martinez Arroyo said the fire was “totally confined” and firefighters expected to be able to extinguish it completely within three or four days.

Authorities believe the fire was intentionally set but say a full investigation into its cause can’t begin until the embers cool.

Firefighters were wary of dousing the fire with too much water for fear of contaminating underground aquifers, state broadcaster TVE said.

By midafternoon Saturday, a few people could be seen on the streets of the Madrid commuter town but a plume of grey smoke was still rising 2,300 feet into the sky.

Known locally as the “tire cemetery,” the dump was declared illegal in 2003 because it lacked proper permits. Authorities since then have been trying to figure out what to do about it.

The online newspaper El Espanol published a document showing Saturday that government-owned industrial waste management company EMGRISA on May 9 proposed that the regional government acquire the dump and convert it into an energy source.