ANTIOCH — Rumors of malevolent clowns on the loose that have been sweeping the internet nationwide made their way Tuesday to the Bay Area, surfacing at schools in Antioch and Oakland and prompting police investigations.

Some youngsters alerted the principal at Dallas Ranch Middle School in Antioch on Tuesday morning to an Instagram message warning that “scary clowns” would be visiting the campus. A similar incident was reported at Black Diamond Middle School.

And in Oakland Unified School District, similar reports of “creepy clown” messages that threaten violence appeared on social media, said district officials. Two threats came on Instagram on the accounts of students attending two district schools, said district police Chief Jeff Godown.

Although they were deemed not credible and believed to be “hoaxes,” police and district staff were “being extra-vigilant” and investigating the threats. The district is also not naming the schools named in the threats, because it’s an active investigation, he said.

“The security of our students and staff is our top priority. We will be monitoring the situation closely and providing extra patrols to the schools named in the rumors and all schools in general,” he said in a statement.

Antioch officers also responded and read the Dallas Ranch posting, but they have not found evidence that it came from a student in the district, Associate Superintendent of Educational Services Adam Clark said, also declining to elaborate on the specifics of the message, citing the ongoing police investigation.

The principal of Antioch’s Black Diamond Middle School received a similar report from students who said they heard clowns would be visiting the campus, Clark added.

The Antioch district decided to send automated calls to all its families about the incidents after receiving a call from a Deer Valley High School official, who indicated that parents were reporting online posts about clowns threatening violence, he said.

In his phone message, Clark urged parents to remind their children not to spread threatening rumors.

He noted that the district’s cyberbullying policy prohibits using any form of technology to frighten students or employees, adding that violators face suspension or expulsion.

In recent weeks, the internet has been rife with reports of “creepy clowns,” people roaming neighborhoods around the country wearing evil-looking clown masks and rattling nerves. Social media postings began to proliferate in late August, when stories surfaced in South Carolina of clowns luring children into the woods. Since that time, creepy clown threats have made their way across the nation, including to California’s Merced and Fresno schools.

Godown said that although the police have not yet been able to determine who posted the photos, it seems that “there is not a unified group that are these creepy clowns, but it could be a lot of individuals, seizing upon the national trend, posting the threats.

“I think a lot of these kids are seeing news of these threats on the internet, and seeing how these get manifested and rolled out…and kind of doing a copy cat thing,” he said.