SAN DIEGO — A report of possible gunshots Wednesday near a coastal North County primary school -- sounds later determined to have likely been a backfiring vehicle -- prompted a roughly hour-long lockdown at the campus while authorities investigated.

Someone reported hearing sounds similar to gunfire in the area of Hope Elementary School in Carlsbad shortly after 9 a.m., according to police.

"Out of an abundance of caution, I called for an immediate lockdown for all students and staff (at the campus)," principal Richard Tubbs said in a prepared statement.

Officers investigating the report contacted several people who described hearing what seemed to be engine backfires emanating from a white pickup truck traveling on a street across a canyon from the Tamarack Avenue school, police Lt. Steve Thomas said.

Investigators found no evidence of gunfire in the neighborhood, according to Thomas.

By 10:15 a.m., the heightened security precautions at the campus were lifted and ordinary daily operations had resumed, Tubbs said.