US smoked salmon supplier Santa Barbara Smokehouse said it is shutting down its facility for six weeks to "completely overhaul" the operation after positive traces of listeria were found on food contact areas within the plant.

"This was a wake up call for us," CEO Tim Brown wrote in a letter to customers dated Jan. 1 obtained by IntraFish. "Our factory is 10 years old, and we feel it is time for a complete overhaul and modernization."

The company said it would keep the factory closed over the next six weeks and "renovate and redesign our entire plant."

"We