DALLAS (CBSDFW.COM) – A contractor installing wiring inside a portable building at Woodrow Wilson High School found ammunition hidden in the ceiling.

Dallas ISD Police were notified immediately and began an investigation, according to a letter sent to parents by principal Michael Moran.

Moran explained in the letter, “As a precaution, we temporarily relocated a class in the impacted portable while police gathered more information. After a thorough investigation, nothing else was found and the campus remains safe.”

School officials said this appeared to be an isolated incident and there is no active threat against the campus.

Woodrow Wilson High School (credit: CBSDFW.COM)