Finding the source of Listeria in a processing plant is tough. It takes environmental sampling to seek out residential Lm and get rid of it. To accomplish that, positive test results lead to further testing (closer to the product) and an investigation into the cause.

And sometimes the source is never found.

A harbor mystery is a problem as the company can’t eliminate the drain, the piece of equipment, or the wall where it’s living and growing. With no source, there’s nothing to fix. And that leaves the company open to problems down the road.

According to the Tri-City Herald, CRF Frozen Foods can’t find the Lm that has been making people sick since 2013.

Gene Grabowski, a consultant acting as spokesman for CRF during the crisis, said the company will turn its attention from trying to find the source of the deadly Listeria pathogen to securing federal approval to restart production.

Bill Marler, managing partner of Marler Clark, a Seattle law firm specializing in food safety, said hunting for Listeria is akin to hunting for the proverbial a needle in a haystack.

“You don’t have to have a filthy, dirty, horrible plant to have Listeria,” said Marler, who is in Washington, D.C., this week to discuss food safety issues with the federal officials, including White House staffers and members of Congress.

“The cleanest plant in the world can be harboring Listeria.”

First, it will conduct its own testing and review CRF’s records. Grabowski said there’s no way to know when CRF might get the green light to resume packing frozen fruits and vegetables.

The company laid off about 250 workers in early June, ostensibly to give them an opportunity to procure seasonal work during the shutdown.

Marler said his firm has been contacted by Listeria patients, though none whose cases have been genetically linked to the strain found in CRF products.