Ex-firefighter Kenton Leong smoked crystal meth before setting three fires in the Makapu'u area in July, he admitted in court this morning.

Leong, 42, pleaded guilty to three counts of second-degree arson as part of a plea deal with prosecutors that calls for a 10-year prison sentence.

Leong was a firefighter for 17 years before he was fired in March for drug use.

"Crystal methamphetamine affects all walks of life, unfortunately including those that are involved with public safety," Deputy Prosecutor Kevin Takata said after the court hearing.

Leong was originally charged with two counts of first-degree arson and one of second-degree arson, but admitted to the reduced charges as part of the plea agreement reached with prosecutors.

Leong "made a full confession" and is dealing with his drug problem, Takata said.

"He's in treatment now and we wish him all the best," Takata said.

Circuit Judge Karen Ahn set sentencing for Jan. 9.

Leong admitted setting three brushfires the morning of July 17 in an undeveloped area on Kalaniana'ole Highway opposite the Hawai'i Kai golf course.

The fires burned more than nine acres of property and were extinguished by five Fire Department trucks and the department helicopter.

Takata said the fires threatened the lives of two campers and a fisherman in the area at the time.

He said the plea agreement balanced the seriousness of the offenses with Leong's history of public service.