New video shows moments after explosion at Walnut Creek senior care facility

We have new video of a fire and explosion that ripped through a senior care facility in Walnut Creek.

Authorities believe smoking materials discarded in the backyard are to blame.

"We could definitely feel the explosion, I mean our whole house shook," says neighbor Jochen Kottgen.  

Kottgen and his daughter recorded video out of their window which showed a fireball rising into the air and the nearby Castle Crest II senior care facility engulfed in flames.

All five of the elderly residents made it out, thanks in part to some teenagers passing by. They've all been taken to other facilities.

Reached by phone, the owner said she's been dealing with the families, and officials all day.

Meanwhile, investigators with Contra Costa County Fire have been working to identify a cause.

They now believe the fire started outside.

"It's been determined that the fire started in the backyard. And it's likely that it was started by carelessly discarded smoking materials," says Steve Hill, Contra Costa County Fire's public information officer.

It then spread, ripping through the senior care home and sending embers flying through the air which caused three additional small fires.

"When we throw into the mix warm weather and windy conditions, we have a formula that is ripe for disaster," says Hill.

Authorities say there were oxygen tanks inside the care home which could account for the explosion. However, they're still investigating.

Neighbors say they're just relieved the residents and staff members are safe.

"The elderly were all pulled out. You know if the explosion had happened first I don't think somebody would have survived in there because the whole house was engulfed right away."