When you buy a dozen eggs at the store are they fresh or are some 30 or more days old? NBC's "Dateline: NBC" reported many processors are mixing the old with the new. And, at least one US Senator is calling for a Federal investigation. But, is it happening here in Utah? The story from Science Specialist Ed Yeates.

Fresh eggs, from hen house to the assembly line. Utah consumers like eggs and most of these will sell quickly. But what happens with leftovers which haven't sold within 30 days? The Government allows processors to mix returned 29-day-old eggs with fresh ones in new cartons with new expiration dates.

Some groups say the practice is misleading and may even compromise safety. But Utah egg producers say "Not to Worry." That practice has been outdated here for the past 10 to 15 years.

((CHRIS SHEPHERD, EGG PRODUCER: "ECONOMICALLY, IT'S NOT FEASIBLE FOR US TO REPACKAGE THEM. IT COSTS US TOO MUCH MONEY TO PULL THOSE EGGS BACK OUT OF THE CARTON AND TO REPACKAGE THEM."))

It's expensive because old eggs have to go back through this candling process to make sure they're still good. And refrigerated eggs can remain safe for three to four months.

But Utah also has a new agenda--a watchdog system which the government now says is a model for the rest of the country.

((LARRY LEWIS/UTAH DEPT. OF AGRICULTURE: "WITHIN THE LAST COUPLE OF WEEKS, UTAH TOOK THE LEAD IN FORGING AN AGREEMENT WITH INDUSTRY AND GOVERNMENT TO ASSURE THAT THE EGG INDUSTRY IS AS SAFE AS ANY INDUSTRY IN THE COUNTRY."))

The Utah Quality Assurance Program monitors egg production and distribution literally from the birth of the chick in the hen house to the final product on store shelves. If large quantities of eggs come back, they end up here at this plant, the only one of its kind in the state.

((ED YEATES, SCIENCE SPECIALIST: "THE MACHINE CAN BREAK EGGS AT THE RATE OF 20-THOUSAND PER HOUR."))

With hair and shirt coverings, workers in the clean room safely pasteurize and repackage the contents of both old and new eggs for larger commercial users.

The State Health Department says despite industry precautions, consumers still must assume final responsibility at home.

It's recommendation: Always use pasteurized egg products to make egg-nogs and salads. When you cook shelled eggs do it thoroughly. And, dont't fry them sunnyside up.