An attempt to recreate an online video stunt led to the evacuation of Swanson Elementary School (6000 block W. 68th Ave.) in Arvada on Aug. 28.

Jeffco School District spokeswoman Lynn Setzer said a backpack had been found at the school with a “strange odor.”

Arvada Fire and Police PIO Jill McGranahan said “a youngster who had stated that he’d brought ‘something’ to school,” was associated with the backpack.

School officials pulled a fire alarm at 9:26 a.m., and later contacted fire and police about the backpack situation.

“The school was immediately evacuated, and according to the principal, it went smoothly,” Setzer said.

The 490-student body of Swanson congregated in the school’s large outdoor field area while the city’s Haz-Mat team investigated the backpack.

“It ended up being benign baking soda and vinegar,” McGranahan said. She added that the student in question — identified only as being 9 years old by the school — was trying to recreate a chemical reaction he had seen in an online video.

Arvada police proceeded to do a full security sweep of the school before issuing the all-clear. Students were ushered back inside around 10:35 a.m.

Setzer said the matter was still under investigation, and that the district would not comment on any potential disciplinary actions for the student.

“Our priority is kids’ safety,” Setzer said.