DETROIT—U.S. auto safety regulators are investigating complaints that the automatic emergency braking systems on more than 1.7 million newer Hondas can stop the vehicles for no reason. The National Highway Traffic Safety Administration says it has 278 complaints that the problem can happen in 2017 through 2019 CR-V SUVs and 2018 and 2019 Accord sedans. The agency announced the probe in documents posted Thursday on its website. In some cases the owners complained of unexpected speed reductions that could cause increased vulnerability to rear collisions. Agency documents say the inadvertent braking can occur without warning and randomly. In six cases, owners told the agency the problem caused collisions with minor injuries. The agency says it’s opening the probe to determine how many vehicles are affected and how bad the problem is. The investigation could lead to a recall. In a statement, Honda said it’s cooperating with the investigation and is …