CLIFTON, N.J. (CBSNewYork) — Several elementary school parents in Clifton say they are upset that they weren’t notified about five students who were detained Wednesday for allegedly plotting an attack on a high school.

The students, ages 10 and 11, attend Clifton School 11. Police said this was not a prank and said the children were plotting to cause damage or detonate a device during a field trip to Clifton High School.

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According to authorities, teachers and administrative leaders found suspicious letters from the students claiming they were going to “attack” the school. The school then notified the Clifton Police Department.

Police said they found a suspicious device, allegedly filled with vinegar and cinnamon, when investigating the threat. Investigators said the device was non-explosive, but the students thought it was.

Investigators said this is an isolated incident and there is no safety issue at the schools.

The five students — four boys and one girl — were detained and later released to their parents.

Thursday morning, many parents at the elementary school were angry to hear about the alleged plot and are demanding answers from school officials.

“We got nothing, I found out on the news this morning and my mother-in-law calling me. Nothing, no phone calls, nothing,” parent Carrie Gould said. “What kids think about hurting other kids and making bombs? It’s really upsetting.”

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“Something this major going on, and you don’t inform the parents?” another mom said. “You’re going to inform me, when? When it’s too late?”

“I’m really surprised by this, we should have been notified,” another father told WCBS 880’s Sean Adams. “I need to speak to the principal or someone in charge — I don’t even know if I’m going to leave them in school today.”

“It’s scary,” parent Juan Oliveros said.

“It’s very disturbing, you know times have changed and it’s a different life now but I guess we’ll just have to cope with it,” parent Pedro Puertis said.

The students have been suspended, but many parents want them expelled, 1010 WINS’ Glenn Schuck reported.

The name of the students involved have not been released, but one mother said “it’s evident to the fifth grade who the kids are.”

Fifth grader Alyson Pineiro said, “They have good grades, they listen and they haven’t really gotten in trouble.”

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CBS2’s Christine Sloan also reached out to the FBI on the incident. A spokesperson said the FBI is aware of the alleged incident and are in contact with the police and other authorities.