The ceremonial cannon that blew apart at the Snohomish High School homecoming game is being scrutinized by experts in a lab.

The goal is to find out what caused the 40 mm cannon, which normally made a loud report and blew smoke rings, to explode and injure five students.

The injured teens all belong to the Marine Corps Junior Reserve Officer Training Corps. The group typically fires the small cannon at the start of each football game and for every Panther touchdown.

ROTC cadets are responsible for measuring and filling nylon bags with 1.7 ounces of gunpowder and then stuffing two of the charges into the cannon’s barrel.

The procedure is supervised by adult instructors.

In addition to examining the cannon in a lab, investigators also are trying to determine whether all protocols were followed the night of the blast.

“I think every rumor that’s come to us that we’ve heard has been investigated, or is being included in the investigation,” said Shannon Parthemer, a school district spokeswoman.

Snohomish police continue to look into the case.

The school district’s insurance carrier is waiting for those reports, and has interviewed students.

“We’ve not ruled anything out,” said Jerry Moran, a litigation specialist with Canfield &Associates in Ephrata. “What we’re doing is looking for the official reports, and we can determine if further investigation is necessary from that point.”

Sophomore Brett Karch was seriously injured in the Oct. 6 blast and underwent multiple surgeries on his leg at Providence Everett Medical Center.

The school district set up a trust fund to help the Karch family with medical expenses.

Karch’s family filed a claim for damages with Mega Life, an insurance carrier that handles the school district’s catastrophic medical coverage for students.

An amount has not been specified.

Reporter Melissa Slager: 425-339-3465 or mslager@heraldnet.com.