By: KDKA-TV’s Royce Jones, Bryant Reed and Meghan Schiller

PITTSBURGH (KDKA) – All Pittsburgh Public schools were on a modified lockdown Friday because of threats on social media.

It was only a half-day for students, but the district said students had to stay inside, only visitors with appointments could enter and all athletics were canceled.

The lockdown was in response to threats of possible violence against schools on social media, the district said.

WATCH: Bryant Reed Reports

“It’s distressing more than anything, that somebody thinks this is a game, this is fun to play,” school board president Sylvia Wilson said. “They’re disrupting the education of children.”

A PPS spokesperson said the threats were similar to those shared on social media earlier this week. The spokesperson added that since Tuesday, six different schools in the district have received threats on social media.

The district said it’s costing valuable time and resources.

“Our school police work in partnership with city police,” PPS spokesperson Ebony Pugh said. “We also then have to notify families. There’s coordination that takes place, the buildings are searched, our teams search the facilities, so it does create a huge response because we definitely take the safety and students of our staff as a top priority.”

School police are working with law enforcement to figure out where the threats came from, and the district said the lockdown was added as a precautionary measure.

“Everyone is trying their best to make sure students and staff are safe in our buildings and are able to learn the way they should,” Wilson said.

WATCH: Meghan Schiller Reports

Many parents, including Mary Tommarello, kept their child home on Friday because she had questions.

“Was there another threat? I didn’t understand. I just wasn’t sure if there were more threats or if they just didn’t know or just because of the amount of threats in general. And not only Pittsburgh Public, I know McKeesport has suffered,” Tommarello said.

The FBI is currently investigating a slew of threats Tuesday against at least a dozen districts in Allegheny County.