Two US teenage students have been accused of plotting to blow up their high school with a homemade bomb.

Alfred Dupree and Victoria McCurley, both aged 17, have been charged as adults with attempted murder and making terror threats after police received a tip off they were planning an attack on Etowah High School in Cherokee County, Georgia.

Police say they found a journal at Dupree's home containing details of the plot and a hit list of targets which included specific students and teachers.

A homemade incendiary device and an unknown powder substance was then found at McCurley's home, officers added.

Officials first became aware of the alleged plot when the school received a tip off on Sunday (22 October) about threats made against students.

Police investigated and arrested Dupree and McCurley. They are due to appear in court on Thursday (26 October).

Sheriff Frank Reynolds said a motive had not yet been determined but revealed investigators were looking into whether the mental health of the teens may have been a factor.

"We have a lot of mental health issues and I think that may have been the cause here," Reynolds told the Atlanta Journal Constitution.

Classmates said the pair, who were not thought to be romantically involved, didn't have many friends.

But Etowah student Sam Jackson told Channel 2 Action News he was shocked by the accusations.

"I just couldn't believe it," he said. "Because I knew both of those kids. They both rode my bus. They released the names today, everyone found out today, and everyone was just shocked."

Dupree's neighbour, Christina Sovine, said she grew up with Dupree and the pair had been close friends.

"He likes to play video games, he's very into video games. His entire family, his dad, stepmother and sister are all very sweet, this is really surprising," she said.

Meanwhile parents of students at the school say they have been left terrified by what could have almost happened to their children.

"The real hero in the whole thing is whoever reported it," said Andy Waldron, a parent of a senior at Etowah. "God bless them because they likely saved lives."

Dupree, of Acworth, and McCurley, of Woodstock, each face three counts of criminal attempt to commit murder and four counts of making terroristic threats and acts, the Cherokee County Sheriff's Office said.