Several Michigan kindergartners were hospitalized after ingesting a 'foreign substance'

• Several Michigan kindergartners were hospitalized after they ingested a "foreign substance."
• Initially, school officials believed they could have been exhibiting signs of carbon monoxide poisoning.

Several kindergartners at a Michigan elementary school were hospitalized on Friday after ingesting a "foreign substance," officials said.

Five students at Edgerton Elementary School, part of the Clio Area Schools district, were transported to a hospital in Flint, Michigan, Superintendent Fletcher Spears III said in a statement posted to Facebook.

As of Friday night, four students remain in the hospital and are in stable condition, officials said.

Initially, the statement said, school officials believed the students have inhaled carbon monoxide. But "the fire department, and later Consumers Energy, have ruled out carbon monoxide or other gasses as the cause," Spears said.

The class was evacuated Friday afternoon after dozens of students showed symptoms of carbon monoxide poisoning, MLive reported.

An investigation has been opened and remains ongoing.

"We believe the students may have ingested a foreign substance," Spears said.

"We will keep you updated on the status of that investigation," Spears told parents and school officials. "Our custodial staff are deep cleaning the room this weekend and we plan to resume school on Monday."

"Please keep all of the Edgerton students and staff in your thoughts and prayers, especially our little ones at [the hospital]," he said. "We wish them a full and speedy recovery."