UPDATED Tuesday, September 11, 2012 --- 8:05 a.m.

STOUGHTON, Wis. (AP) -- A chemistry teacher is home recovering after burning her hand when a science experiment went awry at Stoughton High School.

Superintendent Tim Onsager says the female teacher was conducting a routine experiment to show how chemical reactions happen when a "flash" happened Monday morning.

Onsager says the teacher burned her right palm. She was treated and released from University Hospital.

Some students were showing signs of smoke inhalation and were taken to a local hospital as a precaution. Eventually the entire classroom of about 25 students was checked out at the hospital as a precaution. They have since been released to their parents.

The superintendent says there was no evacuation, and the smoke alarms didn't even go off.

Workers are cleaning the classroom. There was no damage.

Copyright 2012. The Associated Press.

______________________________________________________

UPDATED: Monday, September 10, 2012 --- 11:50 a.m.

Stoughton Schools Superintendent Tim Onsager says the teacher injured in a lab suffered burns to the palm of her hand and has been taken to a hospital.

Onsager says the teacher was conducting a routine experiment. She was showing students a chemical reaction when there was a quick flash of fire. He says the veteran teacher was adding a very small amount of black powder to a beaker and a spark ignited.

A significant amount of smoke filled the classroom.

There were about 25 students in the classroom at the time of the incident. The Superintendent says some of them were coughing or had headaches and were exhibiting signs of smoke inhalation.

As a precaution, all students who were in the class are being taken to Stoughton Hospital. Some are being taken by ambulance, others by bus. At this time, all are expected to be okay.

The school is in the process of contacting all parents and guardians of the students in the classroom.

Authorities are not going to call in a Haz-Mat team. Right now they are in the process of cleaning the classroom. All other classrooms in the school are conducting class as normal.

______________________________________________________

UPDATED Monday, September 10, 2012 --- 10:55 a.m.
Posted Monday, September 10, 2012 --- 10:15 a.m.

Emergency crews have responded to Stoughton High School after a teacher is injured in a classroom.

According to Dane County Dispatch, a 45-year-old female teacher is being transported to UW Hospital after she sustained chemical burns in a classroom. She was heating a powder when the beaker exploded.

NBC15's Brady Headington is at the scene. He reports numerous emergency vehicles at the scene.

A Dispatch operator tells NBC15 News some students were transported for smoke inhalation to Stoughton Hospital.

Stoughton Hospital says six students are being treated; more are on the way. Authorities are uncertain which chemicals mixed; so as a precaution all of the students are changing out their clothes.

Superintendent Assistant Bev Mansfield tells the Associated Press there was a lot of smoke, so about ten classrooms in the science wing were evacuated.

Stay with NBC15.com for continuing coverage of this breaking news story.