The federal government is investigating brake failures on Ford F150 pick up trucks, one of the nation’s most popular car models.

The National Highway Traffic Safety Administration has reportedly received 33 complaints of the brake pedals in Ford F-150 pickup trucks suddenly malfunctioning; in some cases drivers have said they lost complete control of the pedals, which went directly to the floor. From a NHTSA website:

The complaints allege symptoms of brake pedal going to the floor with complete loss of brake effectiveness, brake warning lamp illumination, and/or low or empty master cylinder reservoir fluid level with no visible leakage. Several complaints allege repair facilities diagnosed the problem as brake fluid leaking from the master cylinder to the brake booster.

Thirty-one reports came through in the past year and at least 20 of the reported complaints have come through in the past 7 months, according to a federal website. Federal workers are investigating 420,000 trucks—models with six cylinder engines from 2013 and 2014.

Ford has said it will cooperate with the investigation, according to the Associated Press. NHTSA investigators will be looking into the break issue to see if a recall is necessary.

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