Long Beach police arrested a student at Millikan High School on Wednesday after classmates overheard the student making a threat to hurt people at the campus, authorities said.

The arrest comes on the same day school officials in Long Beach beefed up security after rumors circulated online about a possible shooting plot at Long Beach Poly High School. After an investigation, authorities decided those rumors weren’t credible.

Police said there was no connection between the rumors about Poly and the arrest at Millikan.

School officials did not provide details about what exactly the Millikan student said to catch classmates’ attention, saying only that the student, “made a threat to harm others at the school.”

Those classmates told school staff who called police around 11:15 a.m., according to authorities.

A spokesman for the Long Beach Police Department said he could not release any more details about the alleged threat because the case is still under investigation.

Police are also looking into whether the student had the capability to carry out the threat he allegedly made, police said.

School officials said Millikan students were not in danger at any point during the day.

“We thank the students who came forward with important information,” school officials said in a statement sent to parents Wednesday afternoon. “Please know that we take all threats seriously, and we continue to work closely with our partners in law enforcement to keep our students safe.”

School officials said the student remains in police custody. Authorities did not identify him because he is a juvenile.