Posted: Friday, October 19, 2012 --- 9:50p.m.

BURLINGTON, Wis. (AP) — Chemical fumes at a Burlington elementary school have sent a dozen people to the hospital.

Firefighters arrived at St. Mary's Grade School about 10:20 a.m. Friday.

Fire officials tell WTMJ-TV (http://bit.ly/QCauOZ) that workers had mixed a couple of cleaning solutions that are not supposed to be combined. It was unclear which chemicals were mixed.

About 300 students were evacuated to Catholic Central High School next door. Twelve people were treated at a hospital for inhalation of chemical fumes and eight have been released.

Copyright 2012. The Associated Press.