The five, a retired soldier, two hospital security guards and two other civilians, have not officially been declared suspects in the Oct. 29 killings outside the town of Poso, said Col. Oegroseno, the police chief in Central Sulawesi province.
But there were indications that they may have been involved, he said, without identifying a possible motive or their religious backgrounds. More than 1,500 soldiers and police have been patrolling Poso since six assailants wearing black veils beheaded the three Christian teens as they headed to school. A fourth girl was seriously wounded in the attack.
Indonesia is the world's most populous Muslim nation, but Central Sulawesi has a roughly equal number of Muslim and Christians. The province was the scene of a bloody sectarian war in 2001-2002 that killed around 1,000 people from both communities.
There have been several other bombings and killings in the area in recent years, including a market attack in Poso last May that killed 22 people, most of them Christians.
A detective in Poso, who refused to be identified because he does not have authorization to speak to reporters, said the five men being questioned were arrested in their homes in Poso on Monday.
Ten high-ranking national police officials were involved in the interrogations at the Central Sulawesi military headquarters, he said, reports the AP. I.L.