Smoke spread over the Los Angeles region on Sunday as a fire at a cold-storage warehouse in the Boyle Heights neighborhood continued to smolder for a fifth day.

Firefighters are making progress at stopping the blaze, and the smoke may soon begin to clear, a spokesman for the Los Angeles Fire Department said on Sunday afternoon.

Air quality in central Los Angeles and the San Gabriel Valley continued to be affected by particulates in the smoke. The South Coast Air Quality Management District extended a warning about poor air quality until midday on Monday and indicated that the wind could disperse smoke as far as Riverside and Orange Counties.

In a statement, the air quality agency said that particulates had reached “very unhealthy” levels in some areas on Saturday night and Sunday. The agency was expecting the most significant smoke effects north and east of the fire, and in the San Gabriel Valley and parts of the western Inland Empire.

Major sporting events on Sunday, including the World Cup match between Belgium and Iran at SoFi Stadium and the Los Angeles Dodgers game against the Baltimore Orioles at Dodger Stadium, continued as scheduled.

The blaze at the Boyle Heights warehouse, east of downtown Los Angeles, broke out on Wednesday afternoon and has been challenging to fight because the building’s walls are thick and insulated, like a freezer. Firefighters have also needed to extract ammonia, which was used as a refrigerant, and millions of gallons of frozen food.

But on Saturday night, the fire started to reach parts of the warehouse’s exterior walls, making it possible for firefighters to begin opening the walls and shooting water at critical areas inside that were previously unreachable, said Capt. Jacob Raabe, a spokesman for the fire department. In prior days, there were only small holes in the warehouse.

“If we kept just putting water on the roof, it wasn’t directly attacking the fire that was burning inside,” Captain Raabe said. “It was kind of indirectly cooling it down, but it wasn’t going to fully put it out.”

Firefighters continued prying open walls with heavy machinery on Sunday, he said.

Residents should see an improvement in the smoke conditions during the coming hours and days, Captain Raabe said. “It’s obviously going to take time to get completely extinguished, but you will start to see a significant improvement as we make progress on putting this fire out,” he said.

The roughly 500,000-square-foot commercial building stores about 85 million pounds of frozen food and is owned by Lineage Logistics, a Michigan-based warehouse company.

A Lineage spokeswoman said previously that the company believed the fire started while contractors of the owner of the solar panels on the building’s roof were conducting testing.

Mayor Karen Bass on Saturday issued a declaration of a local emergency to ensure the city has the necessary resources for the firefighting operation. Gov. Gavin Newsom also declared an emergency on Saturday night.

The Los Angeles County Department of Public Health in a news release on Friday advised residents to take precautions if they smelled smoke or saw ash, such as closing windows. Residents who must spend significant time outside should wear an N-95 or a P-100 mask to guard against health impacts, the department said.

Pooja Salhotra contributed reporting.