MILLVILLE, N.J. (CBS) - Authorities are trying to figure out who left backpacks stuffed with weapons — including  a sawed-off shotgun — behind Millville High School in Cumberland County, South Jersey.

Police say members of the school’s cross-country team found the weapons cache yesterday as they warmed up for a meet on a trail near the school.

In addition to the shotgun in the bags, there were shotgun shells, bullets for a handgun, two knives, and two letter openers.

The school was locked down on Monday during a search.  Field hockey and football players were evacuated from nearby fields where they had games or practices, and a tennis match was also stopped.

Millville police say the investigation is ongoing.

Reported by Molly Daly, KYW Newsradio 1060