NEW YORK (CNN/Money) - In another blow to one of automakers' most popular and profitable product lines, the top U.S. auto-safety regulator said sport/utility vehicles and pickup trucks aren't safe enough due to rollover risks and consumers should think twice about buying them, according to a published report Wednesday.

"The thing I don't understand is people, when they choose to buy a vehicle, they might go sit in it and say, 'Gee, I feel safe,'" said Dr. Jeffery Runge, head of the National Highway Traffic Safety Administration, according to the Wall Street Journal. "Well, sorry, but you know gut instinct is great for a lot of stuff, but it's not very good for buying a safe automobile."

Runge, who served as an emergency room physician for 20 years before becoming head of the NHTSA, said SUV drivers are especially vulnerable to fatal rollovers because the vehicles' high center of gravity makes them more likely to tip during sudden maneuvers, the paper reported.

If automakers don't take steps to make SUVs safer, Runge warned, the government could step in to demand changes, according to the Journal.

Runge added that rollovers accounted for just 3 percent of all U.S. auto accidents in 2001 but caused nearly a third of all vehicle-occupant fatalities, and an SUV occupant was more than three times as likely to die as a result of a rollover than an occupant of a passenger car, the paper reported.

Separately, the NHTSA said Tuesday that it opened an investigation into 150,000 General Motors Corp (GM: Research, Estimates). sport/utility vehicles after 36 reports of engines stalling without warning.

The complaints involve 2002 GMC Envoys and 2002 Oldsmobile Bravadas, but the Chevrolet TrailBlazer, which shares the same mechanical parts, is not under investigation.

NHTSA said the reports allege the SUVs stalled at speeds up to 75 miles per hour, causing steering and braking to fail. In some cases the engines could not be restarted and the vehicles had to be towed.