A fire in LA has been burning for days. What’s taking so long to put it out?

Los Angeles firefighters are on their sixth day of battling a fire at a massive warehouse near downtown that stores frozen food.

Smoke has billowed from the warehouse, which was covered in solar panels and insulated like a freezer, filling the air surrounding the roughly 500,000-sq-ft (46,450-sq-meter) facility.

The blaze that broke out last Wednesday has been especially challenging for firefighters due to the nature of the facility operated by Michigan-based Lineage in the Boyle Heights neighborhood east of downtown. Firefighters haven’t been able to enter the building and are instead fighting the blaze from outside.

Authorities said a large warehouse fire can typically be put out in a day, but in a cold storage facility, it can take weeks. Jaime Moore, the chief of the Los Angeles fire department, said there are about 85m lbs (38.6m kg) of frozen food stored inside.

Here’s what to know:

What caused the fire?

The cause of the fire has not been determined, Lineage said in a statement on its website.

The company, which provides temperature-controlled warehouse space to food and beverage makers, believes the fire began when subcontractors were working on solar panels on the roof, the statement said.

Lineage is working with fire officials investigating the blaze, the statement said.

Why is it taking so long to put it out?

It will at least take a few more days to extinguish the fire, said Jamie Stewart, a Los Angeles fire department spokesperson.

Fires in cold storage facilities often burn for weeks because their heavily insulated ceilings, roofs and walls make them difficult to extinguish, Stewart said.

Firefighters have not been able to enter the building due to the danger posed by floor-to-ceiling heavy-duty steel rack shelving, he said. They also have been unable to quickly ventilate the roof due to the insulation, which is what they would typically do to release gas and smoke and gain visibility inside a warehouse, he said.

In this case, firefighters have been stripping away exterior walls on certain sides of the building and dousing it with heavy streams of water, he said.