Carbon particles from a car's exhaust sparked the fast-moving 400-acre brush fire near Lake Jennings that shut down Interstate 8 and prompted mandatory evacuations, Cal Fire Chief Tony Mecham said.
"We have determined the cause of the fire is related to carbon particles from a vehicle exhaust, but we do not believe it is the cars that were actually on fire, that's separate from this incident," Mecham said. There were three separate vehicle fires in the area, but, according to Mecham, they were not related to the Jennings Fire.
The fire sparked around shortly after 1:30 p.m. Tuesday afternoon when Cal Fire, Lakeside Fire and Alpine Fire officials responded to multiple 911 calls reporting a brush fire.
In less than an hour, the fire had grown from five acres to 100 acres, Cal Fire officials said. By 4 p.m., it had grown to 400 acres. Drivers on State Route 52 could see the smoke as far as Tierrasanta and Mission Trails.
For several hours, Interstate 8 was shut down so crews could battle the fast-moving flames, which sent a plume of thick, gray smoke above East County.
The fire burned at a rapid rate of spread in an area described as having medium fuel. The fire initiated a response from several fire agencies in San Diego County, Mecham said. Seven air tankers, four helicopters, 43 engines and a little more than 250 personnel were involved in battling the blaze.
As of 6 a.m. Wednesday, Cal Fire reported the fire was 30 percent surrounded.
A mandatory evacuation order was issued for Viewside Lane, Peutz Valley and the upper end of Harbison Canyon in the Hunter Pass area.
Reverse 911 calls were being made to residents affected by the evacuations.
Joan MacQueen Middle School at 2001 Tavern Rd in Alpine has been set up as an evacuation site. An evacuation center at Granite Hills High School in El Cajon was shut down after 6:30 p.m.
According to the Alpine Union School District, students who are in Extended School Service were evacuated to Joan MacQueen and parents have been notified.
The San Diego Red Cross is providing water and snacks for evacuees.
At least five homes were threatened at one point, Mecham said. Strike teams were requested for structure protection along Montana Serena, a road along a ridge south of Interstate 8 and east of Rios Canyon Road.
Cal Fire officials say they hope to let residents back into their homes by Tuesday night, if possible.
NBC 7's Llarisa Abreu said heat, humidity, and the wind are driving factors in fires like the Jennings Fire.
Tuesday afternoon, temperatures in the area were around 82 degrees and dry. The humidity was around 38 percent.
Abreu said the higher the humidity, the better the conditions to fight fires. Winds are calm in the area--around four to eight-MPH with gusts of 16-MPH.
Mecham said the heat conditions and dry brush fueled the fire.
"It does not take a lot to get a spark into the grass," he said.
Once the flames had subsided, crews found the piece from the exhaust system responsible for the blaze at the origin of the fire, where I-8 meets Highway 80.
Crews reopened westbound I-8 just before 8 p.m., but eastbound lanes remain closed. The closure for eastbound traffic begins at Lake Jennings Park Road, CHP said.
Motorists should expect heavier traffic on southbound State Route 67 in Lakeside, SDSO said. Traffic was backed up to Scripps Poway Parkway.
Mecham said fire agencies are working with CHP to have all eastbound I-8 lanes open by late Tuesday night.
Firefighters will stay on scene overnight and for the next few days to mop up the fire, he added.
San Diego Metropolitan Transit System issued an update that all Route 864 trips will end at East County Square until further notice. This means there will be no MTS service to Viejas due to the wildfire.
Are you and your family prepared for a brush fire?
County officials advise residents to download the free emergency smartphone application SDEmergency and follow three key steps.
GET READY: Do your 100-foot defensible space in advance
GET SET: Have an emergency plan. Pack your car when Santa Anas arrive.
GO: When told to leave, leave.
The San Diego Humane Society advised residents to take any pets with them, should they need to evacuate.
For updated information on the fire, you can also call 211.