2nd threat in 1 week at Oak Grove Elementary

ALISO VIEJO, Calif. (KABC) -- Oak Grove Elementary School in Aliso Viejo has been hit with the second threat in less than a week. The school was placed on a "shelter-in-place" alert Thursday.

It was not clear if the two threats were related.

Orange County sheriff's deputies rushed to the campus and began investigating a threat Thursday morning. The Capistrano Unified School District says the order was lifted about an hour and a half later after deputies found nothing.

"A police officer and his dog sniffed around the classroom a few times," said 5th-grade student Ashley Nylander.

Parents were notified by phone about the threat and the "all-clear." Many waited in large groups to pick up their children, some feeling like they were being left in the dark.

"We know that they've got to keep certain things under wrap. It would be good to know what type of threat it was," said parent Julie Nylander. "Was it a bomb threat? Was it a substance threat? Is it a threat to kill?"

Frustration is mounting because this is the second threat the school has received in a week. Authorities received a similar threat on Friday. Parents say they didn't learn about that threat to the school until Sunday night.

Many parents chose to keep their kids at home after the first threat, prompting a call Wednesday night telling them the school was safe and students should come to class.

"We didn't trust what we were being told, and today proved that that questioning of it was probably accurate," said parent Dan Clementino.

Extra security was added at the school this week.

A district spokesman told Eyewitness News by phone that they're doing the best they can in this situation.

"We are not able to provide information, A, That we don't have or, B, Information that should be provided by law enforcement," said Stephen Nichols.

An investigation into both threats continues. Some parents are concerned about the safety of their children.

"It's unfortunate but we're not even sure if our kids will come back to school," said Clementino.

The District said classes are scheduled as normal for Friday, and parents will be notified of any new information.