PORTSMOUTH, N.H. – The parent company of Portsmouth’s Redhook Brewery, where an employee was killed when a keg exploded as it was being cleaned, has hired an independent investigator to try to determine what caused the accident.

In a message sent to members of the brewing industry on June 1, Craft Brew Alliance, Inc., CEO Terry Michaelson said the investigator who his organization has hired will assess the keg and the cleaning equipment that was involved.

Investigators from the federal Occupational Safety and Health Administration are also investigating the April 24 explosion that killed Ben Harris, 26, of Newington.

“Although we are still awaiting conclusions from OSHA, we recognize the importance of sharing information about the accident with the brewing industry in hopes of preventing similar accidents,” Michaelson wrote in the message obtained by Foster’s Daily Democrat.

Investigators say Harris was in the process of emptying the keg with pressurized air when it blew apart at the seams. The plastic keg was not owned by Redhook or any Craft Brew-affiliated breweries, the company said.

“For years, this process for emptying kegs has been performed without incident in a substantially identical manner at the Redhook Brewery and all of our other breweries,” Michaelson wrote in the message.

There were no witnesses to the 7 a.m. explosion

OSHA said the Redhook brewery in Portsmouth has never been cited for a workplace safety violation.

Michaelson said the company was planning to brew a memorial beer to celebrate Harris’s life.

“More than anything, we hope that the information we’re able to share in the wake of this tragic accident contributes to greater awareness about safety and to safer work environments throughout the industry,” he said.