As flames continued to rage out of control in San Bruno, fire crews from outlying cities and agencies were responding to help fight the massive blaze that has left at least nine people burned and destroyed a number of homes.



Four air-tankers, two smaller attack planes and 25 fire engines from the California Department of Forestry and Fire Protection were headed to the blaze, the agency said.



Off-duty firefighters, some of them without their protective gear, were battling the blaze alongside overwhelmed crews from the small San Bruno Fire Department, according to news reports.



Huge orange balls of flames were billowing into the nighttime sky. Residents reported a huge shake, as if an earthquake had struck when the blaze broke out.



The radiant heat from the flames could be felt several blocks away, according to residents.



The blaze, which broke out shortly after 6 p.m., may have been caused by a large gas-line explosion, said a spokesman with Pacific Gas and Electric.



The Blood Center of the Pacific declared an emergency and asked for people to donate blood Friday morning.



At San Francis Hospital in San Francisco, a major burn center, two patients were in critical condition, but medical crews were gearing up to treat more patients.



"We do expect more victims," said hospital spokeswoman Theresa Edison.



-- Robert J. Lopez

Photos: Fire in San Bruno