Police said Friday they have issued a murder arrest warrant for one of two missing Southern California teens and believe charred and fragmented human remains found in his Riverside County backyard belong to the other youth.

Police are seeking Jose Campos, 17, and arrested his stepfather and mother, Jose and Maria Seym, late Thursday on suspicion of being accessories to murder, said Hemet police Capt. Tony Margis.

Police have also issued an arrest warrant for Felicia Sharp, 17, and a 21-year-old man named Rene Lopez-Fregozo, Margis said.

Authorities believe the charred remains found last month in a firepit behind Campos' house are those of 17-year-old Adrian Rios, although they are awaiting the results of DNA testing on some of the remains, including a severed human foot. Results could take several weeks.

Margis said investigators believe Rios was shot and was dead when his body was placed in the firepit. They have not recovered a murder weapon and have not determined a motive, he said.

Six people were in Campos' home during the alleged murder or immediately after the crime, said police Chief Richard Dana.

The investigation began on Nov. 17, when Rios' mother, Elodia Lopez, reported him missing.

Lopez last saw her son two days before, when he went to Campos' house to watch a football game, authorities have said.

When he didn't come home, his mother went to Campos' house. She found no one home but saw a bloody sneaker in the backyard and found drag marks in the dirt. She told police the sneaker looked like her son's shoe, according to a search warrant affidavit filed in the case.

Police also noted a number of flies clustered on a saturated area of the ground, according to the warrant first obtained by The Press-Enterprise newspaper.

Sharp, who is Campos' girlfriend, was initially reported missing, but she came forward last week and told police she had been staying with her mother, who is separated from her father.

Margis said detectives do not believe she was truthful during a two-hour interview last week. She has since run away, he said.

Also missing is the Campos family's white Chevy Tahoe.

Hemet is in a rural area about 90 miles southeast of Los Angeles.