The rash, similar to others reported elsewhere in Connecticut and throughout the nation, developed quickly, Superintendent Dr. Evan Pitkoff said Thursday.

"It had a quick onset and the number of cases climbed to 70 by the end of the day," Pitkoff said.

Both the Torrington Area Health District and the Connecticut Department of Public Health were called in to investigate the outbreak, with the Torrington district handling the investigation.

James Rokos, Director of Health at the Torrington Area Health District, said his office would perform "a very complete inspection of the entire building" Friday, and emphasized that there was no reason for parents to panic.

"We are about as positive as we can be this is not any kind of bio-terrorism or anything like that," Rokos said. "It's a mystery, a complete mystery. We did a thorough inspection (Thursday) and didn't find anything unusual."

While the health department did not mandate the school closing, Pitkoff said he and other officials determined closing the building for a day to give the health district three days to investigate was the proper decision.

The first reports of an infection came in Wednesday when a student complained of a rash. The same student returned to school the next day with a very obvious skin condition and was sent home. By the end of the day both students and teachers had some sort of skin rash.

The affected students were sent home Thursday and will not be permitted to return to school until they have received clearance from a medical doctor, preferably a dermatologist Pitkoff said.

This is not the first mysterious rash to hit Connecticut or the nation. The Centers for Disease Control and Prevention reports similar incidents in 14 state, including Indiana, Mississippi, Oregon and Georgia in addition to another outbreak in Connecticut.

The first reported incident occurred in Indiana on October 4, 2001. That report was followed by others in Virginia and then in January and February.

Rashes have been primarily limited to elementary schools, although there have been reports of rashes among a few middle and high school students and a number of teachers.

Officials are investigating the cause of the rash outbreaks, though diagnoses thus far have included eczema, chemical exposure and poison ivy.

Fifth Disease has also been blamed in several cases.

Pitkoff said the school was expected to reopen on Monday.