TARZANA (CBSLA) – An undisclosed threat forced the closure of a small private school in Tarzana Friday.

The Woodcrest School, a K-8 school located at 6043 Tampa Ave., informed parents in an email that the school would be closed Friday due to a possible threat. The nature of the threat was not confirmed.

Los Angeles police received notification of the criminal threat at about 5:30 p.m. Thursday, according to the Los Angeles Times.

Parents were advised in the email to tell their children that a “plumbing issue” had forced the closure, the Times reports.

It’s unclear if police have identified the source of the threat.