Supervalu Inc. received a big slap on the wrist from federal regulators for serious food safety violations at a seafood processing facility in Pennsylvania — violations not typically seen at such a large operation.

The U.S. Food and Drug Administration sent a warning letter last week to the Eden Prairie-based grocery retailer citing six violations at one of the company’s Denver, Pa., wholesale distribution centers that, if not fixed soon, could be shut down.

A failure to properly regulate the storage temperatures for different types of fish, which protects against harmful pathogen growth, and the absence of an allergen prevention program, which safeguards against cross contamination, are among the violations.

In a statement Wednesday, Supervalu said “We take food safety very seriously and have already enhanced our existing seafood [hazard analysis] plan for the Denver, Pa., distribution facility.”

The FDA closely monitors seafood establishments, said Ted Labuza, a professor of food science at the University of Minnesota, noting that more than 50 percent of warning letters issued in the last year were against seafood facilities. Warning letters are the last chance for a business to make a correction before the government shuts down the operation.

“These are usually against small, little places that … don’t realize that they have to have a [hazard analysis] plan in place, that have strict regulations,” Labuza said.

This severe of a warning letter is rarely issued to large corporations like Supervalu because they usually have strict protocol for following regulations. “That’s why this surprises me,” he said.

Companies have been cited for worse offenses, according to Labuza, but the lack of proper temperature controls is a “real big problem” for fish.

According to the FDA’s letter, which was made public this week, some of Supervalu’s suppliers might not have been storing seafood products at the right temperature during transportation. Supervalu said it would correct such situations by not accepting delivery from the supplier should that happen again. The government agency suggested the company terminate relationships with those suppliers who don’t follow protocol.

“Temperature control on fish has been very, very important to the FDA,” Labuza said. “In the last four to five years, the FDA has gone much more aggressively after food companies. A consumer assumes when they open a product package, the product is safe.”

Supervalu must respond with a correction plan within 15 days of receiving the warning letter.