Investigators: Boys playing with fire will face arson charges for burning down Oregon ballpark

Onlookers watch the Civic Stadium burn in Eugene, Ore., Monday, June 29, 2015. The stadium was approved by voters in 1938 during the Great Depression and opened that same year. (Andy Nelson/The Register-Guard via AP) (The Associated Press)

Beth Wirth, left, pulls her sons Emmett Wirth, 2, and Anderson Wirth, 5, in a wagon during a visit to the still smoldering Civic Stadium, Tuesday, June 30, 2015, in Eugene, Ore. A fire destroyed Eugene's historic Civic Stadium on Monday evening and prompted the temporary evacuation of a two-block area, the fire chief said. (Chris Pietsch/The Register-Guard via AP) (The Associated Press)

Eugene Springfield Fire arson investigators begin the process of finding a cause of the Civic Stadium fire Tuesday, June 30, 2015, in Eugene, Ore. A fire destroyed Eugene's historic Civic Stadium on Monday evening and prompted the temporary evacuation of a two-block area, the fire chief said. The stadium was approved by voters in 1938 during the Great Depression and opened that same year. (Chris Pietsch/The Register-Guard via AP) (The Associated Press)

A massive fire that destroyed Eugene's historic Civic Stadium was caused by four boys playing with fire who fled when the flames got out of control, investigators said Thursday.

The panicked boys jumped a chain-link fence as the flames spread Monday night, hopped on their bicycles and fled, said arson investigator Steve Williams.

The parents of a fifth boy who left before the fire tipped off police on Wednesday.

The four are to be charged with arson, Police Chief Pete Kerns said at a news conference Thursday. One is 10, the others 12.

The stadium was a jobs project in the Great Depression but hasn't been used since 2009 when the minor-league Eugene Emeralds left. A group determined to keep it from being demolished for a supermarket had bought it, taking out a $3 million insurance policy.

The boys probably didn't intend to destroy the park when they used a lighter on debris in the press box above the stands behind home plate, Williams said.

But they haven't given coherent reasons for why they were playing with fire, and they may not understand the magnitude of their actions, he said.

"I don't know if you've ever talked to a 10- or 12-year-old boy recently, and you don't get a whole lot of rational information out of them," Williams said. "It's: 'Why did you do that?' 'I don't know.'"

The fire sent flames shooting twice the height of the structure, and smoke was visible throughout the city, which is about 100 miles south of Portland.