Police told ABC affiliate WFAA on Tuesday that a contractor found ammunition in the ceiling of Woodrow Wilson High School.
Principal Michael Moran said in a letter to parents that the contractor was installing wiring Monday when he saw the ammo hidden in a portable building, the Dallas Morning News reported. A class in that building was moved to a different location Tuesday while authorities investigated.
The contractor did not find anything else, but school officials said they might increase security as a precaution, according to WFAA.
The ammunition was found the same day authorities discovered ammunition in a toilet at Life School Red Oak Elementary south of Dallas.
The two events do not appear to be connected.