With 11 students suffering influenza-like symptoms Friday, Galt High School shut down early as officials scoured the school grounds in search of an environmental trigger.
School officials said they found nothing in their classroom-to-classroom sweep to explain the sudden illnesses. They concluded a fast-moving virus was likely the culprit, a district spokeswoman said.
Initially, seven students became sick on campus, and four more succumbed to the flu-like symptoms such as fevers and vomiting after being dismissed early.
Officials had swiftly canceled classes out of caution for the well-being of the more-than 1,000 students enrolled in the high school, said Jean Malmgren, executive assistant to the Galt Joint Union High School District superintendent.
Of the seven who fell ill at school, three were taken to hospitals in Sacramento; one was sent to a hospital in Lodi. The remaining three were released to their parents, Malmgren said.
"Originally, it was thought it could be pinpointed to some doughnuts," Malmgren said. "But then they couldn't specifically say that was the case without a doubt."
Galt police officers, hazardous material officers, Fire Department personnel, the superintendent and administrators combed the campus for a source of the outbreak.
They checked food on the campus but found no signs of contamination.
"They speculate that it's a very strong strain of a virus," Malmgren said.
Classes are expected to resume Tuesday, after the three-day holiday weekend, she said.