In a trouble for US carmaker Ford, the National Highway Traffic Safety Administration said on Friday started a review of reports that some exhaust gases, including carbon monoxide, could enter the passenger compartment of some Ford Explorers.

This is seen as a safety problem and it has already led to customer complaints. A customer has also filed a legal suit against the company.

The NHTSA said in a statement that it knew about the complaints involving Ford Explorers from model years 2011 through 2014 from some Ford Explorers owners. The owners claimed about experiencing exhaust fumes or other strange odors in the cabin. The agency said in a statement that it was "reviewing all available data and will take appropriate action as warranted."

Angela Knutson, the owner of a 2013 Ford Explorer, filed a lawsuit in Florida federal court on June 9 in which she said that a defect in hundreds of thousands of Explorers could cause "lethal quantities of carbon monoxide" to enter passenger cabins. It happens when the vehicle is on the move and this is a risky proposition for the occupants of the vehicles.

A Ford spokeswoman said the company was reviewing the case and the company would take actions to resolve this issue as soon as possible. Knutson told reporters that she decided to file the lawsuit on behalf of a proposed class of owners of Explorers from model years 2011 through 2013.

The lawsuit said that in 2012, Ford issued a technical service bulletin to dealers acknowledging that some Explorers from model years 2011 to 2013 "may exhibit an exhaust odor in the vehicle with the auxiliary climate control system on."