WHEATON, Indiana — A senior at Wheaton North High School last week ejaculated into a bottle of ranch salad dressing and left it on a condiments cart in the upperclassmen’s cafeteria, school officials said Thursday.

The student returned the bottle to the cafeteria’s condiments cart.

Sodexho, the school’s food service provider, requires that condiment containers be emptied and washed every other day.

However, Principal Jill Bullo said company officials are unsure whether the container was washed Wednesday after lunch. If it was not, students would have been exposed to its contents during the last two lunch periods Dec. 6 and all five on Dec. 7, after which the container definitely would have been cleaned, Bullo said. At the very least, students would have been using the bottle’s contents during fourth- and fifth-period lunch on Dec. 6.

The student confessed to contaminating the bottle Tuesday, school officials said, adding it is unknown whether anyone ate the salad dressing or has become sick from it, school officials said.

Apparently the student bragged to friends about what he had done during his lunch period Dec. 6, and one of them told school leaders Tuesday, said Gary T. Catalani, Wheaton Warrenville School District 200 superintendent.

“I don’t believe that they thought it to be true, but students were talking about this rumor,” Bullo said.

In a letter mailed Wheaton North parents Thursday, District 200 outlined what course of action the school will take regarding the incident.

Catalani said the district is working with Wheaton police, who said an attempted aggravated battery arrest is imminent.

“An act occurred that could have physically harmed someone at the school, but no one was physically harmed,” police Cmdr. Joseph Eversole said.

The school’s punishment for the student was not disclosed.

“We’ve taken very severe measures against this student,” Catalani said.

Sodexho has discontinued its use of smaller bottles for condiments and has started using larger containers that would make it difficult for a student to steal.

Most students’ reactions on Thursday were of dismay and anger.

Senior Brian Corcoran learned about the incident Wednesday.

“I was very surprised and appalled and embarrassed that this could happen,” he said.

Freshman Andrea Daun said she would never eat cafeteria food again.

“You’re supposed to feel safe enough to eat at school, but this makes you feel disgusted,” she said.

Senior Jon Kinsey said although he did not know the student very well, he did attend classes with him.

“He was kind of a crazy kid and never complied with school rules,” Kinsey said.

The DuPage County Health Department, in consultation with the Illinois Department of Public Health, issued a statement Thursday about the incident.

“The risk of acquiring a sexually transmitted disease or other disease from the ingestion of food contaminated with semen is considered extremely low,” the statement said. “We are not aware of any documented cases of hepatitis B, hepatitis C, HIV or other sexually transmitted diseases that have been spread through this means.”

However, the person responsible is undergoing medical evaluation, the statement said. If he has an illness that may pose a risk to others, information will be provided to the parents of potentially exposed students.