October 18, 2018—U.S. safety regulators are investigating why Ford pickup tailgates can open unexpectedly while the trucks are moving, reported The Detroit Free Press.

The National Highway Traffic Safety Administration opened an investigation into thousands of F-250 and F-350 Super Duty trucks from the 2017 model year, according to the report. The agency says In documents posted Wednesday that it has five complaints from owners about the problem. It says unsecured loads could spill onto roadways.

The documents show Ford sent a service bulletin to dealers in October 2017 saying that the problem is caused by water getting into electrical wiring. 

Ford says it's cooperating with NHTSA and will move quickly to recall vehicles if data indicates a safety issue. In a rare move, the agency listed the number of vehicles involved in the investigation as "confidential." Ford spokeswoman Elizabeth Weigandt said the company did not request it; an NHTSA spokesman said he would look into the matter.