An air tanker that nose-dived in Northern California, killing all three crew members, was repaired four years ago for cracks in one wing, a representative of the plane’s owner said Tuesday night.

The downed C-130A Hercules, operated under contract with the U.S. Forest Service, had just completed a pass over the blaze Monday when its wings snapped off and the fuselage plunged in Walker, Calif.

The tail section of a C-130A air tanker sits just off a highway in Walker, Calif. The nation's C-130A air tankers were grounded Tuesday after Monday's crash that killed all three people aboard. The plane lost its wings and nose-dived while being used to battle a wildfire.

George Petterson, the lead National Transportation Safety Board investigator at the crash scene, said he was not aware of the earlier wing problem, but that it would be examined.

“I have no idea if that’s related to what we’ve got,” he said.

The nation’s C-130A tankers, workhorses of the firefighting fleet, were grounded Tuesday in the midst of what could become one of the worst fire seasons in history.

Fires were burning in across nearly a half-million acres of tinder-dry forest and brush in seven Western states. Thousands of people have been forced to flee and more than 60 homes have been destroyed, most of them in Colorado. A wildfire about 40 miles south of Denver grew by 7,000 acres Tuesday night to 120,000 acres, forcing about 2,000 more people to evacuate their homes.

The C-130A that crashed Monday was fighting a 15,000-acre Cannon fire north of Yosemite National Park. Investigators were trying to determine whether a practice campfire set by Marine trainees started the blaze Saturday.

The plane’s operator, Hawkins & Powers Aviation Inc., notified the Federal Aviation Administration in April 1998 that an inspection discovered two 1-inch cracks in the surface or “skin” of one of Lockheed-built plane’s wings, according to an FAA document obtained by The Associated Press.

Records show the 46-year-old aircraft passed its last major inspection in October.

FAA representatives did not immediately return calls Tuesday night.

The C-130A tankers are only a fraction of the National Interagency Fire Center’s fleet of 43 contract planes. Nancy Lull, a spokeswoman for the fire center in Boise, Idaho, said the five planes will be grounded for at least two days while their safety is evaluated.

“They will be shut down until a preliminary investigation can determine what happened to this particular aircraft is unique or that there is some sort of structural problem with all C-130s,” said Ed Waldapfel, a Forest Service information officer at the fire center in Boise.

Authorities identified the crash victims as pilot Steven Wass, 42, of Gardnerville, Nev.; co-pilot Craig Labare, 36, of Loomis, Calif.; and crew member Michael Davis, 59, of Bakersfield, Calif.