GM may have been told about its faulty ignition switches by rental car companies seven years ago after several unusual accidents.

One of the questions surrounding the faulty ignition switch controversy at General Motors is when did the automaker know there was a problem? It may have been at least seven years ago and the death toll related to those vehicles may rise as a result.

Two rental car companies sent notices to GM suggesting the automaker investigate fatal crashes where the airbags in the vehicles did not deploy – vehicles recalled by the maker this February, according to Bloomberg News.

Seven years ago, an investigator for the parent of Alamo Rent A Car, Vanguard Car Rental USA, contacted GM to inquire about a fatal rollover accident in California. The driver was killed and the airbag failed to deploy in the Chevy Cobalt he was driving.

A claims adjuster wrote to GM and said even though the cause of the crash wasn’t immediately known, “due to the serious nature of this accident we feel that it is imperative that you open a claim and inspect this vehicle for possible defects,” according to a review of documents obtained by Bloomberg News after a Freedom of Information Act request.

However, Vanguard wasn’t the only company that expressed concern. Enterprise Holdings Inc., Avis Budget Group Inc. and Hertz Global Holdings Inc. also had Cobalts in their fleets that crashed.

GM and the U.S. National Highway Traffic Safety Administration officials swapped information during an eight-year period beginning in 2005 related to cars stalling and airbags failing to deploy.

(GM smacked with new lawsuit alleging 29 deaths. For more, Click Here.)

In the files GM submitted, there were 30 crashes involving 37 fatalities in the Cobalt and the Saturn Ion. They add to mounting evidence that GM didn’t put forth a concerted effort to fix the problems…and the complaints about them were increasing.

(Click Here for details about the role of looser credit in auto sales.)

The maker had already received complaints from consumers by the time the rental car companies chimed in. Over time, automotive reviewers and even its own dealers and mechanics joined the chorus of complaints about abnormal crashes that have since been linked to a faulty ignition switch.

(To see why Gen Y is buying more new cars than Gen Xers, Click Here.)

The files show many missed opportunities to ask questions and connect disparate events, according to Bloomberg, the very type of evidence that is supposed to be routed to and investigated by the NHTSA’s Early Warning Reporting system.