PORTLAND (AP) – School officials are looking into whether an exercise in which fake bombs were placed on school buses needed prior authorization.

Officials said the schools’ transportation director, Kevin Mallory, got the idea while attending a national conference on bus safety in Austin, Texas. Five wooden packages wrapped with a note suggesting a terrorist bomb threat were placed randomly on buses at the transportation depot on Nov. 6.

The exercise was meant to test whether drivers were thoroughly checking their buses, officials said. But bus drivers and others in the Portland district are criticizing the approach.

Superintendent Mary Jo O’Connor said Mallory did not get authorization to conduct the bomb exercise. But still unclear is whether he needed to get that approval. Officials are also looking closely at the language in the note.

“The block of wood had a note attached to it, which we believe was a serious error in judgment,” O’Connor said before Wednesday night’s school committee meeting. “We’re taking it seriously and doing a full investigation.”

The superintendent did not say whether anyone found the packages and was not sure if Mallory had prepared drivers for a bomb drill. She said, however, that Mallory had stressed routine safety procedures during meetings earlier this year.

“These safety drills did not just come out of nowhere,” O’Connor said. “The underlying purpose was the importance of doing a safety check.”

Mallory referred questions to Joline Hart, director of human resources for Portland Public Schools. A message to Hart was not immediately returned Thursday morning.