PAYNESVILLE, Minn. (AP) -

Officials say they have found no environmental cause for an illness outbreak that sickened more than two dozen students at Paynesville Area Secondary School.

The school was declared safe after a hazardous materials team swept the building Tuesday.

In a letter to parents and students, Paynesville Superintendent Bob Huot says the district plans to sanitize the building Wednesday and secondary students can stay home. Elementary students also will have the day off due to transportation routes and staffing. School will resume Thursday.

Huot told the St. Cloud Times that seven students felt woozy during a choir concert Monday night and were taken to a hospital, but felt fine by Tuesday morning.

Students started feeling sick again as classes resumed Tuesday, so the school sent students home.