A former New Market volunteer firefighter has pleaded guilty to felony charges stemming from a series of arsons.

LOS ANGELES—Investigators from multiple agencies gathered yesterday at the spot where a gigantic arson fire erupted in a national forest as they built a murder case that they plan to present to prosecutors. Arson investigators are trying to determine who ignited a fire that has torched more than 230 miles of the Angeles National Forest on the edge of Los Angeles and killed two firefighters.

A Rockingham County grand jury will consider arson charges against two former New Market volunteer firefighters accused of setting several fires.

Field day will go on, but the summer won’t be the same at George Mason Elementary School in Richmond after an early-morning fire destroyed the playground. The fire, called in at about 3:30 a.m. yesterday, engulfed most of the metal structure, burning away the blue-and-red plastic coating and melting the sliding boards into pools of yellow, mulch-infused muck. The one-alarm fire was quickly extinguished, but the $70,000 playground is a complete loss.

A 27-year-old man was convicted yesterday in Louisa County of setting fire to his twin brother’s home in Louisa County after an argument over a cell-phone bill, according to authorities. Joshua A. Follin was found guilty of arson for a fire Dec. 18, 2007, that destroyed a garage, two cars and several recreational motor vehicles, officials said.