A San Jose warehouse burst into flames early Thursday, causing multiple explosions, smoke and billowing fire, and a roof to collapse during massive firefighting efforts.

The large blaze was one of four fires crews contained on Thursday. The other fires included a two-alarm condominium fire on Trevino Terrace off of Trinidad Drive and two small fires.

San Jose Fire Capt. Barry Ehlers said the warehouse fire escalated into five alarms just after 7 a.m. The blaze was first reported about 5:30 a.m. at 1325 Julian Street near 28th Street.

Firefighters contained the blaze just before 8:45 a.m. Fire crews from Sunnyvale, Santa Clara and Mountain View assisted San Jose in battling the blaze.

RAW VIDEO:5-Alarm SJ Warehouse Fire Causes Explosions, Roof Collapse

In just 70 minutes, the fire raced across 125,000 square feet, the length of a city block.



Craig Johansen lives just feet away in one of the 15 homes forced to evacuate.



“Just mountains and mountains of flames,” Johansen said. “It looked like a tornado of flames. It was just unbelievable.”

While firefighters were able to prevent the inferno from destroying homes, it did get close enough to destroy a few garages, sheds and vehicles.



No one was hurt.

Firefighters say the biggest challenge was the massive size of the warehouse, and the five businesses inside, each with its own possible set of possible combustibles.



“You’re looking at roofing and plumbing supplies inside, and all could have had material to fuel a fire,” San Jose Fire Department Captain Cleo Doss said.

A part of the building that collapsed is marked with a sign that reads "Dave's Hay Barn." A sign on another part of the building reads "Vintage Roof Tile." Ehlers said the fire was reported by two Vintage Roof Tile employees.

PG&E cut off power to 4,000 customers as crews battled the flames. Among the PG&E customers without power is San Jose High School, where classes continued without lights. Power was restored to the school around 10 a.m. Officials said it could take several hours to get power restored to all 4,000 customers. Anne Darling Elementary School was also without power for several hours.

Officials issued a "shelter in place" for nearby homes, while the California Highway Patrol advised that motorists in the area drive with their windows shut to prevent breathing in the fumes.

The area is mostly industrial, but nearby schools, Rocketship Discovery Prep and Empire Garden Elementary, canceled classes for the day. And just before 7 a.m., the California Highway Patrol closed the northbound and southbound sections of Julian Street near U.S. Highway 101 because of the fire.

That became a traffic nightmare for those commuting in the area near the McKee Road exit just at the start of the early morning commute.

PHOTOS: 5-Alarm Fire Rages at San Jose Warehouse

Firefighters told San Jose High School staff that there were no toxic fumes released by the fire, but to be on the safe side, physical education classes are being held indoors today, San Jose Unified School District spokeswoman Traci Cook said.

Investigators are still trying to determine the cause.

The warehouse fire follows on the heels of another San Jose fire reported about 3 a.m. That fire went to three alarms at a home on south 17th street. The two people inside were able to get out safely.

Homeowner Stan Rubin said he and he his wife would have been "toast" without their smoke detectors." Below is a photo of the Rubin home.



Bay City News and NBC Bay Area's Geoffrey Eisler and Marianne Favro contributed to this report.