(Adds details from local authorities on bombs, suspect's plan)
May 26 (Reuters) - Authorities in northwestern Oregon said on Sunday that a teenager arrested for producing what authorities called explosives for a Columbine-style attack on his high school had meticulously planned his foiled bombing.
"He was definitely following a detailed checklist," said Captain Eric Carter of the Albany police department about the 17-year-old, Grant Acord. "It appears he had a systematic, well-documented plan, this was not just an errant note."
Acord, a West Albany High School student, was arrested on Thursday night after police received a tip that he had produced a bomb and planned to detonate it at school. Carter said Acord was arrested at his mother's home in north Albany on Thursday evening without incident.
During a search of the residence, police officers found six home-made bombs, including pipe bombs, Molotov cocktails and napalm bombs under the floorboards in the suspect's bedroom.
Carter also said the police discovered diagrams of Acord's school, which "led us toward the conclusion that he was planning a Columbine-style attack" a reference to the 1999 Columbine High School massacre in Colorado where two teenagers shot a teacher and 12 other students to death before committing suicide.
"That claim will be demonstrated in the evidence we will provide," said Benton County district attorney John Haroldson, whose office has jurisdiction over Acord's case. "The suspect was working based on a very methodical process."
"This was not driven by emotion, this was driven by a mission."
Police conducted two searches of West Albany High School on Thursday evening and on Friday, the latter a more extensive inspection using a canine bomb detection unit from the Oregon State.
Authorities said a detailed affidavit listing the evidence against Acord would be released on Tuesday. Under Oregon law, as Acord likely faces charges of attempted murder, if the case goes to court he would be tried as an adult.
Acord could not be reached for an immediate comment on Sunday.
Albany, Oregon, is about 70 miles (110 km) southwest of Portland. (Reporting By Nick Carey; Editing by Scott Malone, Maureen Bavdek and Nick Zieminski)