Three Fresno Unified School District fifth-graders were suspended after they plotted to put rat poison in their teacher's coffee, the Fresno Teachers Association said Thursday.

The students also laced a cupcake with poison, said FTA President Greg Gadams. Fresno Unified spokeswoman Susan Bedi confirmed that three students allegedly plotted to poison a teacher's coffee in mid-December, but she was unaware of allegations that a cupcake also was allegedly poisoned.

Immediate disciplinary action was taken against the students, Bedi said. But she would not confirm whether the students were suspended.

However, Bedi said that "something of this nature would result in suspension with recommendation for expulsion."

(Follow-up story: Union says incident shows need for stepped-up counseling of students)

The female teacher, who has not been identified, did not drink the coffee allegedly laced with rat poison because one of the students involved had second thoughts and knocked the cup off her desk, Bedi said.

District officials notified Fresno police about the alleged plot, she said.

Bedi did not disclose the gender of the students or the school where the incident allegedly occurred.

Gadams said the teachers' union appreciated the district's swift action in removing the students from the campus but was concerned that the Fresno Police Department did not arrest the fifth-graders or pursue charges.

In a statement issued later Thursday evening, Chief Jerry Dyer said police went to Balderas Elementary School on Feb. 8 to investigate the poisoning allegation. Because of the nearly two-month delay between the alleged incident and the investigation, there was no physical evidence, Dyer said.

But once the investigation is completed, the Police Department will consult with the District Attorney's Office to determine whether charges should be filed against the students, who are 10 and 11, he said.

It was unclear Thursday night why the investigation did not begin before Feb. 8.

School district officials notified the teachers' union about the alleged plot after a parent sought praise from the principal for "[their] child saving the life of [the] teacher," the FTA said.

The teachers' union has called a news conference for 10:30 a.m. today at the Mariposa Mall on M Street to talk about how the alleged poisoning plot is the latest example of dangerous conditions stemming from inconsistent enforcement of discipline.

But Bedi said the district continues to make school safety a high priority.

"Staff and administration are extremely vigilant in investigating alleged violations of the district's zero tolerance policy, and students who violate this policy are disciplined in a swift and appropriate manner," she said.