PINEWOOD SPRINGS, Colo. -- Fire investigators have determined what started the Big Elk Fire.

A faulty catalytic converter on a Jeep was found to be the ignition source. The converter was found on a vehicle that investigators had been looking for since the fire stated.

The U.S. Attorney's office said that the driver of the vehicle won't face charges because an effort was made to put the fire out and it was reported in a timely fashion.

Sunday's thunderstorms helped slow the growth of the 4,100-acre Big Elk Fire, but lightning from those storms also sparked another smaller blaze in the area, 7NEWS reported.

The smaller fire is now burning just over the ridge in Spring Gulch. It is causing residents in the area some concern, but so far it has not grown much or damaged any structures.

The larger Big Elk Fire is about 25 percent contained and no homes have been destroyed, the Larimer County Sheriff's Office said.

A historic cabin in one of Colorado's original settlements -- Homestead Meadows -- was destroyed. This area is located at the end of the 3-mile Lion Gulch trail and is home to eight historical structures that were built between 1889 and 1923.

BIG ELK FIRE INTERACTIVE ARTICLE: Plane In Previous Crash Owned By Same Company VIDEO: Eyewitnesses Describe Crash VIDEO: Working Life Of Tanker Pilots VIDEO: Role Of Air Tankers VIDEO: Evacuee Tells His Story SLIDESHOW: Air Tanker Overview SLIDESHOW: Big Elk Fire - Day 1 SLIDESHOW: Big Elk Fire - Day 2 Big Elk Fire Map FLASH: Fire Causes And Protections DISCUSSION: Should Old Planes Still Be Used? RESOURCES Evacuation Tips Smell Smoke? MAP:Fire Point Of Origin USFS: Big Elk Fire Larimer County Web Site Current Colorado Wildfires Clickable Colorado Wildfires Map

On Sunday, firefighters spread foam on several hundred homes as the fire advanced into a subdivision and crept within yards of structures.

About 225 homes in the Big Elk Meadows, Little Valley and Lake Pasture Ranch subdivisions are still evacuated, and people in 400 to 500 more houses were told to be ready to leave at any time.

Some residents were allowed to return home Sunday after authorities reopened U.S. Highwy 36 between Lyons and Estes Park.

Officials said the blaze is human-caused. Fire investigators were looking for two white men seen along Larimer County Road 47 where the fire started Wednesday. They were driving a white Jeep, either a CJ-7 or Wrangler.

The cost of fighting the fire so far is $576,000.

Cleaning Up Air Tanker Wreckage

While fire crews tackle the new blaze and the Big Elk Fire, recovery crews continue to bring out debris from the wreckage of an air tanker that went down.

Authorities say there may be some small delays on Highway 36 in the Lion's Gulch area today while heavy equipment is used to bring out more parts of the PB4Y.

The PB4Y World War II-era bomber split apart in midair last Thursday as it prepared to make a slurry drop.

The left wing came off and the plane broke into several pieces by the time it crashed into the ground, instantly killing the pilot and the co-pilot, authorities said.

The main body of the plane crashed on the north side of the fire, within 100 yards of Highway 36. Parts of the wreckage even fell on the highway, 7NEWS reported

The severed wing and the engine from the plane were found about one-fourth of a mile away from the main wreckage.

Photographs of Thursday's air tanker crash show a fireball coming from the 47-year-old plane. A photo student at the Art Institute of Colorado took dramatic pictures of the accident. The photos, taken by Matt Inden, were shown on 7NEWS. The photos were also made available on the Web by the Rocky Mountain News.

Coroners have identified the two crew members who died on board that plane as 39-year-old Rick Schwartz of Ulm, Mont., and 56-year-old Milton Stollak of Cathedral City, Calif.

On Sunday, slurry-dropping air tankers were up in the air for the first time since they had been grounded immediately followind the fatal crash.

Investigators continue to look into the cause of the crash.

Plans Drawn Up For Possible Estes Park Evacuations

The Larimer County sheriff's office has updated an existing evacuation plan for the town of Estes Park, which was about 4 to 4.5 miles from the head of the fire Sunday, spokeswoman Eloise Campanella said. The town has about 5,400 people, according to the 2000 Census, but the population swells in the summer with tourists.

Campanella said the plan divides the town into four zones, each of which would be evacuated in turn if fire is spotted.

Previous Stories:

July 22, 2002: Why Are Older Planes Used To Fight Fires?
• July 21, 2002: Big Elk Fire #1 Firefighting Priority
• July 20, 2002: Big Elk Fire Expands Again
• July 20, 2002: Pilot Killed In Crash Was Newly Married
• July 19, 2002: Big Elk Fire Now 2,500 Acres And Growing
• July 19, 2002: Internal Memo Questioned Aircraft Maintainance
• July 18, 2002: Plane In Previous Crash Owned By Same Company
• July 18, 2002: 2 Killed When Air Tanker Fighting Big Elk Fire Crashes
July 18, 2002: Wildfire Near Estes Park, Pinewood Springs Lays Down
• July 12, 2002: Forest Service Under Fire From Widow Of Airtanker Pilot
• June 18, 2002: Investigation Begins In Fatal Air Tanker Crash
• June 18, 2002: 3 Die In California Air Tanker Crash
• June 17, 2002: Air Tanker Crashes Fighting Sierra Wildfire