MELBA — Five Melba elementary school students were taken to the hospital after some fainted during a music rehearsal in the high school gym Monday.

Unsure of what caused the students to become ill, officials called hazardous materials crews to the scene and evacuated about 400 students and staff from Melba High School around 2 p.m.

Melba School District Superintendent Bob Larson said three students fainted during the practice, which had been going for about 20 to 30 minutes. Between 75 and 100 students were in the gym at the time.

Larson theorized that one of the students locked knees during the rehearsal, causing that student to faint and others to follow suit.

"One goes down; others see that and go down," Larson said.

Two other students did not faint but complained of feeling sick, Larson said. The five students were taken to an area hospital and released around 5:30 p.m., he said.

Larson said he appreciated emergency personnel's concern for the safety of the students and the hazmat team's response to check out the building's safety.

"The EMTs didn't want to take a chance with that. Everything checked out; no issues at all with the air quality or anything," Larson said.

Crews cleared the building around 6 p.m., Canyon County Paramedics Deputy Director Scott Tucker said. The spring program for which the students were practicing still took place in the school's gymnasium Monday night.

"We appreciate all the assistance from the local fire departments and hazmat to help us make sure our children are as safe as they can be," Larson said.