Some police say their Ford Motor SUV police cars are leaking exhaust fumes into their vehicles, causing officers to suffer from carbon monoxide poisoning.

Federal safety officials are looking into the allegations surrounding the Ford Police Interceptor, a version of the Ford Explorer modified for police use. They have yet to open a formal investigation.

The National Highway Traffic Safety Administration has already investigated more than 150 complaints from Ford Explorer owners about the smell of exhaust fumes in their SUVs. Ford has settled a class action lawsuit related to those complaints.

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One officer in Newport Beach, California, passed out while driving his Interceptor in September 2015, according to police accident report. Brian McDowell's Interceptor swerved across two lanes of oncoming traffic, nearly hitting another car head on, and crashed into a tree at 55 mph. McDowell has yet to return to work and he is suing the automaker.

The Austin, Texas, police department has already pulled 37 Interceptors from service. It has even hardwired carbon monoxide detectors into the Interceptors that are still on the road. The detectors have signaled high levels of carbon monoxide, an odorless gas, in at least six cases. The city is considering whether to replace its 400 or so Interceptors, although that would be difficult since they make up about 60% of its fleet.

"The safety of our officers and employees is our number one priority," said city spokesman Bryce Bencivengo.

One Austin officer, Zachary LaHood, said he narrowly avoided crashing into another vehicle in March when he was overcome with fumes. He was able to stop the car in a parking lot without an accident. He has sued the automaker, and at least three other officers from other states are talking to his attorney about bringing their own cases. The potential plaintiffs include a 30-year old officer from Northern California who suffered a stroke, which can be the result of carbon monoxide poisoning.

Ford (F) says it is investigating the complaints, but so far has found no evidence of a problem.

"We have investigated and not found any carbon monoxide issue resulting from the design of our Police Interceptor Utility Vehicles," Ford said in a statement. "We know police modify these vehicles, which can contribute to exhaust-related issues. We have provided instructions to help seal these modifications and are ready to inspect any vehicles with this concern. Also, we will cooperate with NHTSA on this investigation, as we always do."

The attorney for McDowell and LaHood said this is a serious problem, for both police and the general public who drive the Explorer.

"It's only a matter of time before an officer or member of the public gets killed," said Brian Chase.

Ford said the Interceptor and Explorer are different vehicles that have different engines, among other things, which means that a problem in one wouldn't necessarily be found in the other.

Officials at NHTSA confirm that the agency is investigating both the police cars and the Ford Explorers.

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The attorney who sued Ford over the Explorer exhaust complaints said his testing showed unsafe levels of carbon monoxide in the Explorer. But even he said they did not rise to levels that could cause people to pass out while driving.

"If [police] are getting enough carbon monoxide to pass out, there's something very different with those vehicles," said John Uustal, who brought a federal class action suit in 2014.

But Uustal said the level of exhaust getting into the Explorer still poses a health hazard, and can cause illness from prolonged exposure.

"Ford has never considered this a safety issue, but I believe it is," said Uustal, who recently reached a settlement with Ford on the case. He said his initial client, a fire fighter from Fort Lauderdale, had used a carbon monoxide detector from his department in his car and found 120 parts per million of the gas. He said other tests he conducted as part of the suit regularly found 30 and 35 ppm. That is above what's considered a safe level for prolonged exposure, said Uustal.

-- CNN's Tony Marco, Tina Burnside and Jason Morris contributed to this story.