BOSTON -- If you're in the market for low-fat hamburger meat, you know to check the label because fat content and the prices vary.

NewsCenter 5's consumer reporter Susan Wornick reported that generally, the lower the fat content, the higher the price.

"As I was cooking it, it was rendering a lot of fat," said Sharon Bennett.

Bennett bought hamburger at Johnnie's Foodmaster in Melrose, Mass., that was supposed to be 90-percent lean. But when she cooked it, it didn't look 90-percent lean, so she went back to the store.

"I saved the fat and brought it back to the store where they gave me another pound of meat and it turned out to be the same," she said.

Bennett was concerned that Johnnie's Foodmaster wasn't labeling their hamburger accurately, so she contacted NewsCenter 5.

A test of four packages of hamburger ranging from 10 percent to 27 percent fat found that they all contained a different amount of fat than labeled. Two samples had much less than advertised, and two had much more. The most egregious difference was the hamburger marked as 10 percent fat contained more than 15 percent fat.

"It looks almost as though they were taking the same lot of intermediate fat ground beef and just putting four different labels on it," said Dana Krueger of Krueger Food Labs.

Johnnie's meat manager John Cremens said that unlike bigger chain stores, they "make their own hamburger" in the individual stores. He said that it is "not an exact science" and "sometimes there are mistakes."

Johnnie's own random testing by an independent firm in 2004 showed eight mistakes in 50 samples.

Mislabeled meat can be costly for consumers because low fat meat is more expensive. The meat from Johnnie's marked 10 percent fat was $4.29 a pound -- 60 cents more than meat containing 20 percent fat.

"If somebody's labeling it as containing less fat than it actually has, they're able to command an artificially high price," said Krueger.

According to federal law, meat isn't legally mislabeled unless it is greater than 20 percent in excess of what it said on the label. There are no imposed penalties for mislabeled meat because no one is policing the industry on that particular issue.

NewsCenter 5 also tested hamburger from Shaws, Star and Shop & Shop grocery stores and found no discrepancies.