What happened at North Star High School? Here's what we know.

BOSWELL ― Officials still didn't know Friday afternoon what sickened several North Star High School students Thursday morning.

There are no indications carbon monoxide or any other gases, nor any chemical or environmental issues, caused the students to become sick, according to North Star School District administrators, the Somerset County Department of Emergency Services and the federal Environmental Protection Agency.

Multiple rounds of testing were conducted in the school throughout the day Thursday, and an environmental response team from the EPA in Philadelphia arrived late Thursday. On-scene coordinators and chemists from the EPA conducted specialized tests and air sampling in various areas of the high school, including the school library, where the first students became ill.

None of those specialized air sample tests have shown any levels of concern, said Kevin Clark, an on-scene coordinator with Region III of the EPA.

North Star administrators said Friday morning they were aware of 26 students who were evaluated on Thursday for symptoms of lightheadedness, dizziness and lethargy after being in the school. However, UPMC Somerset records show the hospital received a total of 41 patients, all of whom were treated and released as of 8:15 a.m. Friday, according to Sarah Deist, senior manager, public relations for UPMC.

District Superintendent Louis Lepley said in addition to working with local fire departments and emergency crews since the beginning of the incident, North Star has been in contact with UPMC Somerset, various toxicologists and specialists, personnel from Peoples Gas, the Somerset County Department of Emergency Services and the state and federal environmental agencies to confirm that there were no air quality issues at the high school.

“Everybody’s been working together and collaborating through the entire day yesterday to make sure that our students were safe and make sure that our building was safe,” he said.

“Throughout the day, we had ongoing testing (and) we also deferred questions to the emergency specialists to ensure that we could remain open and continue the education process. That message was relayed that we were ‘good to go’ and that there didn’t seem to be a threat of gases (carbon dioxide, carbon monoxide) or anything else that would endanger students and/or staff.”

A second round of testing was continuing on Friday “in an abundance of caution,” Clark said.

An update posted Friday afternoon on the high school's Facebook page said that, "To date, all air quality readings have been negative for any chemical or environmental conditions of concern inside the building."

Lepley said the district administration does not yet know why the students became ill Thursday, but since the EPA’s additional test results show no issues or concerns, plans are to reopen the high school on Monday for classes as usual.

There will be additional carbon monoxide detectors installed around the school for continued monitoring, and the school’s police officer will be conducting an internal investigation as well, he said.

“We hope that parents, students and staff will be put at ease,” Lepley said. “Our No. 1 concern is the safety of our students and staff. We wouldn’t ever put our students or staff members in harm’s way.”

Studying the sun: How did Berlin Girl Scout Elliot Blubaugh become an Eclipse Investigator?

What happened at North Star High School?

Students at North Star High School were under a flexible instruction day Friday while officials investigated.

According to Somerset County 911, the Boswell and Stoystown volunteer fire departments and the Somerset Area Ambulance Association were dispatched at 8:28 a.m. Thursday to the high school because several students had passed out.

Then at 12:12 p.m., the Somerset County Career and Technology Center called Somerset County 911 to report more students from North Star who were bused there for vocational training were also feeling sick.

Cloudy or not? What does the forecast look like for Monday's total solar eclipse? Here's what we know.

The students were examined, and some were taken to UPMC Somerset for further testing, according to an announcement released on social media by the North Star School District late Thursday.

“Based on information first shared by area hospitals, initial testing focused on carbon monoxide; however, results did not indicate elevated levels in the building,” the announcement read.

“As of 10:30 p.m. (Thursday), all further air quality sampling and investigation results have been negative. Responding agencies continue to investigate the building using specialized equipment looking for a potential cause for the illness.”

High water: Where did the heavy rain cause problems in Somerset County? Here's a look.

In addition to the initial fire department and EMS personnel response, the Somerset County Department of Emergency Services, Pennsylvania Emergency Management Agency, the Pennsylvania Department of Environmental Protection and the U.S. Environmental Protection Agency were at the high school overnight Thursday conducting additional testing.

This article originally appeared on The Daily American: No cause found so far for multiple North Star students with sudden illness