SEATTLE -- Outdated baby formula on local grocery store shelves -- it's not supposed to be there, but our KIRO 7 Consumer investigators found it.

Baby food and baby formula are the only foods required by the FDA to have a "use by" date printed on the cans and jars.

When that date comes and goes, that food and formula is supposed to be pulled.

But we found outdated food and formula still on the shelves -- and still for sale.

We took our hidden camera inside local grocery stores.

We found that of the 29 grocery stores, drug stores and other retailers, nine had baby formula on the shelves that was past the "use-by" date.

We found a can of powdered formula with a use-by date read August 2006. But it was still for sale in early January when we bought it.

We also found a jar of baby food bought just two weeks ago. The use by date almost one year old: March, 2006.

MORE ON THIS STORY File a complaint with the FDA

Some local moms we spoke to are outraged -- concerned that they haven't checked the dates, worried what they might be feeding their babies.

"I'd be concerned with the grocery store, too, that wouldn't be checking that, and keeping it out on the aisles for people to purchase."

In many families, infant formula is the sole source of nutrition for the baby.

And if it's expired, the baby isn't getting what he or she needs.

"The real problem if a baby gets enough of an inadequate formula is they are not going to grow well and it can affect overall health."

Melissa Mortensen says over time, the nutrients and vitamins in the formula degrade.

The amount of nutrients like zinc, calcium and protein listed on the label is not what the baby is getting.

"Powdered infant formula is not sterile, and we worry that microorganisms might get a chance to grow beyond what a young immune system could fight off," Mortensen said.

And while busy parents, toting a fussing child throughout the store, maybe tempted to just grab a can of formula and dash to the check out stand, it's often worth a quick look to check the date on the bottom of the can.

"If I had thought about checking the expiration date, I actually would probably let them know I'd take it up to the front and say did you know this had expired."

So who is responsible for pulling the outdated formula from store shelves?

Ultimately, it's you, the parent. Because none of the agencies involved are watching.

If parents do buy formula that is outdated, they can always return it to the grocery store where they bought it.