DENVER -- According to experts at Carfax, you could be driving a rebuilt wreck and not even know it.

There are millions of salvaged cars for sale, but many sellers do not reveal their true history before taking the buyer's money.

"I just saw this crack. It has been glued. Not a very clean job of fixing the mirror," said Jeri Cretti.

She got a bad feeling the first time she saw the used car her daughter Jinny bought.

"I thought, Oh my gosh. What have they done here?" she said.

Cretti's 16-year-old daughter paid cash for the 2000 Mercury Cougar after answering an add on Craig's list.

"The price was $3,800," said Cretti.

She said the car started falling apart as soon as her daughter drove it away.

"They had super glued (the airbag compartment) shut. She did not notice this at all until she was driving home and it started popping open," she said.

They later noticed both airbags are missing, the battery is dead and there are transmission problems.

"And, after learning more about this car, it had been totaled and rebuilt," Cretti said.

It gets even worse for the young, first-time car buyer, her mom said.

"The title is still in the name of the insurance company when it was totaled. Since then it was sold to two other people. We're the third buyer," she said.

"The second you drive off the lot the balance tips to the seller and you have to prove they misled you. Better to walk away from the deal," said Carfax communications director Larry Gamache.

Gamache said buying a rebuilt wreck without knowing it can hurt the buyer both financial and physically.

"Airbags don't deploy, electronic systems don't work, people play games with the wires. You need to protect yourself," he said.

Carfax lined up three very similar looking vehicles currently for sale on a used car lot to see if anyone could tell which one had been involved in an accident.

Volunteers checked out every inch of the vehicles, which included a Pontiac, a Saturn and a Chevrolet, looking for any visible defect.

All of them were used cars, but only one had been in a wreck and repaired.

Each volunteer was asked to stand next to the car they thought had been in an accident.

The Saturn got a vote, so did the Malibu, but the majority of volunteers chose the Pontiac, and they were right.

Although the majority of volunteers guessed the right car, Carfax experts said you can never tell just by looking if a car has been involved in an accident or salvaged.

The recommend a Carfax vehicle history report combined with a mechanic's inspection of the vehicle before the buyer makes a purchase.

The Carfax report costs $25 but only shows accidents that have been reported.

Since many accidents are never reported, a mechanic's inspection is strongly recommended prior to purchasing a used car.

Carfax experts said there are several signs a car has been salvaged, including uneven gaps between doors or the hood.

They also recommend buyers lift up plastic parts and pull up the carpet to check for hidden welds or damage to the frame underneath.

Some of the common problems associated with previously wrecked vehicles, according to Carfax, are:

Title washing. Title documents may be altered to remove a salvage brand and obtain a clear title from another state.

Air bag fraud. Scam artists are known to replace deployed air bags with phony or non-working air bags to cut costs.

Structure or frame damage. As little as 8 millimeters can compromise a car's structural integrity, which also may affect many of the car's safety features.

Odometer rollbacks. The odometer also may be rolled back to further inflate the perceived value of the vehicle.

Car clipping. Some rebuilt wrecks are actually two different cars welded together.

If you would like more information about avoiding rebuilt wrecks or how to obtain a Carfax report, Carfax.com