Carfax announced this week that millions of used cars with unfixed recalls were sold online in 2013.

The annual study shows over 3.5 million cars were put up for sale online last year with "an open safety recall," according to a company press release.

The states with the most recalled cars for sale online in 2013 were Texas, California, Missouri, Florida and Ohio.

Almost one-third of total were in those five states, though every state has unfixed recalled vehicles.

"Open recalls are still a major public safety issue," said Larry Gamache, communications director at Carfax, according to the press release. "In fact, our research indicates that more than one in ten used cars for sale online has an open recall. It's another reminder that consumers, especially those shopping online, need to know as much as possible about a used car before they buy. This includes if an open recall or other potentially dangerous issue exists. It helps make our roads safer for everyone."

Federal safety regulators recently released a new vehicle recall label created to help consumers identify a valid recall notice from an automaker.

The idea of the new sticker is to help consumers differentiate an actual vehicle recall notice from junk mail or misleading sales material.

"The most important thing about open recalls is knowing there is one," said Gamache. "We found that in 42 states, consumers shopping online for used cars in March and April stand the greatest chance of buying one with an open recall. Whenever and wherever you shop, make sure to look for open recalls and have them fixed. Almost every recall will be fixed for free at your local franchise dealer."

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