PITTSBURG — Four people have been arrested after more than one social media threat was directed at Pittsburg High in recent days, police said.

All four are younger than 18 years old, police said. Three of those arrested are current students at the school, while the fourth is a former student at Black Diamond High School. They all were booked into juvenile hall.

Police originally looked into a Twitter post on Sept. 14 and investigated it through the weekend, Capt. Steve Albanese said earlier this week. They eventually determined the threat wasn’t credible, he said.

On Tuesday night, police posted on social media that they had investigated “several” social media threats “over the past few days.”

None of the four whom police arrested were equipped with any weapons to carry out acts against the school, police said, adding that the arrests were made because of the nature of the threats.

Police didn’t specify what the threats said. Staff from the Pittsburg Unified School District also worked to identify those involved in the threat, police said.

Five full-time security officers help patrol the high school and middle schools, police said, along with regular police staffing near the school grounds.

“We also need help from parents. It is vital that parents speak with their children about safe and responsible use of social media,” police said in a statement. “Inappropriate or threatening statements and content online is treated the same as offline. This includes making threatening statements towards establishments or people. Both actions and words have consequences.”

These arrests followed the arrest by Clayton police of a student at Diablo View Middle School on Tuesday on suspicion of identity theft and making criminal threats. They say that student hacked into a social media account and made an unspecified threat.