Anchorage police have arrested two 18-year-old men in connection with Monday evening's fire at a South Anchorage school, saying they left a burning piece of paper at the playground and it ignited the blaze.

According to police spokeswoman Jennifer Castro, Robert Charles Yaskell and Riley Dean Borello-Poythress are both charged with third-degree criminal mischief, a felony, as well as misdemeanor counts of criminally negligent burning and failing to report or control a fire in the incident at Bowman Elementary School.

"Further investigation found that they had lit paper on fire on the playground and left the playground after the paper was ignited," Castro wrote. "It was reported to police that they were burning a 'love letter' from an ex-girlfriend."

Castro said the nature of the relationship that ended in the letter's burning wasn't immediately clear Wednesday. She said police had spoken with several witnesses before making contact with the defendants.

"When we spoke with them, they were cooperative with police -- but they did not initially report the fire to us," Castro said.

Anchorage firefighters responded to the school, near Lake Otis Parkway and O'Malley Road, shortly after 8 p.m. Monday. According to fire spokesman John See, it took two crews at least half an hour to bring the fire under control because of combustible rubber mulch used to cover the space beneath the equipment.

Castro noted that the men weren't charged with arson, which involves a deliberate attempt to ignite a blaze.

"They did not indicate that they were trying to light the playground on fire," Castro said.

Anchorage School District spokeswoman Heidi Embley said Wednesday that the total estimate for replacement costs from the fire, which destroyed two pieces of playground equipment, came in at about $21,000. Three playground fires last summer at Alpenglow Elementary, Taku Elementary and Aquarian Charter schools did nearly $110,000 in total damage.

Yaskell and Borello-Poythress were remanded to the Anchorage jail on Tuesday, Castro said.