A fire at a 1m sq ft warehouse complex continued to burn out of control in California early on Friday, as authorities warned the blaze could take days to extinguish and may contain toxic hazards.

The raging inferno was pumping thick black smoke up in billowing clouds as flame and a red hot glow were visible beneath from aerial images. The fire has destroyed the medical equipment warehouse in Tracy, in northern California, and prompted evacuations of other nearby facilities, with no injuries reported.

Authorities are still investigating the cause of the fire, which ignited on Thursday afternoon at the large distribution center for Medline, a major medical-surgical products provider in Tracy, about 55 miles east of San Francisco. It spread across the street into a FedEx facility, where crews were able to block it, according to the fire chief, Randall Bradley, of the South San Joaquin county fire authority.

A sprinkler system that appeared to be broken and low water pressure in hydrants at the facility hindered the firefight, Bradley said. The issues appeared to be with the warehouse’s water system, not the city’s. Low humidity, high temperatures and strong wind also posed challenges, according to Bradley.

Antonio Talavera, a Medline employee, told ABC7 the fire rapidly tore through the site. “Within 30 minutes, half the building was covered already.”

Officials had evacuated a large portion of the area as the wind heightened the risk of spreading embers, said Sgt Michael Richards, from the city’s police department. Three secondary fires broke out from the embers, according to ABC7. No homes had been evacuated by early Friday. The enormous warehouse is in a large industrial park that also houses fulfilment and distribution centers for Amazon, Home Depot and FedEx. Medline said all its employees and other personnel at the site were accounted for, the Associated Press reported.

“We are coordinating closely with local authorities and first responders as we assess the fire’s impact and will share more details as they become available,” a spokesperson for the company said in a statement.

Medline is a supplier of latex gloves, masks, surgical instruments and other medical supplies that were key during the Covid-19 pandemic.

The effects of the fire on the company’s supply chain remains unclear.

“Immediately following this incident, Medline activated a command center and a network contingency plan and began incorporating secondary and tertiary distribution centers,” a spokesperson for the company said in an emailed statement. “Product distribution previously supported by the Tracy facility has been reassigned and it is in the process of being deployed to other facilities within our regional network to help maintain service and support customer needs.”

The spokesperson did not answer a question about the fire’s origins.

Officials are evaluating air quality and possible impacts to residents of the area, said Dan Arriola, Tracy’s mayor.

Authorities encouraged “sensitive” groups including children, older adults and those with respiratory conditions to limit their smoke exposure by staying indoors.

An investigation into what started the fire remains under way.

The Associated Press contributed reporting