Investigators trying to determine cause of fire that destroyed part of storage facility in Pacheco

PACHECO, Calif. (KGO) -- Kelly Van Shaik, who manages Pacheco Mini Storage, says no one is being allowed to the back storage area that burned on Tuesday.

"It's not safe. We just need to keep it clear," explains Van Shaik.

The fire broke out just after 2:30 p.m. in a grass area near the intersection of Highway 4 and Interstate 680.

Witnesses say the flames grew to as high as the nearby palms trees, with smoke and flames visible for miles.

The fire quickly spread to the large storage units at the back of the 500-unit facility. Close to 50 of the units burned.

The staff spent part of Wednesday morning speaking to investigators, but the cause of the fire is still unknown.

"We don't know. I mean, a cigarette butt, a spark from a car, the construction that's on the freeway, it could have been anything," says Van Shaik.

Van Schaik says there is a homeless encampment nearby, which has caused them problems in the past.

"Garbage, trash, their stuff, breaking into the property, cutting the fence, I mean all of the above," she says.

Van Shaik says insurance will cover some of the damage, but that the hard part will be making calls to those who rented units that were destroyed.

"Their lives are in there. Their kid's stuff, their stuff. It's just hard. The phone calls are going to be really tough today," says Van Shaik.

The staff was told it could take up to two weeks before a cause of the fire can be determined.