WASHINGTON (Bloomberg) -- Federal regulators are escalating an inquiry over complaints that certain Fiat Chrysler Automobiles NV vehicles can roll away when a driver thinks the transmission has been set to park.
The probe into three Fiat Chrysler models affects about 856,300 cars, according to a document filed by the National Highway Traffic Safety Administration's Office of Defects Investigation.
The rollaway car incidents resulted in 121 alleged crashes, according to the document, with 30 leading to reported injuries.
The majority of complaints centered upon the 2014-15 Jeep Grand Cherokee, while the other models involved were the 2012-14 Chrysler 300 and the Dodge Charger with a 3.6-liter engine.
The regulatory inquiry expands a probe opened in August addressing 14 complaints that 2014-15 Grand Cherokee vehicles had rolled away after a driver intended to park them.
An engineering analysis was opened "to assess the scope, frequency and safety-related consequences of the alleged defect," according to the document.
More than 300 complaints about rollaway problems have been reported to regulators and the manufacturer, according to the document.
The cars have an electronic gearshift made by ZF Group that may not provide drivers with clear enough feedback in all cases about the gear they're in, according to the document.
"We're fully co-operating with the investigation," said Eric Mayne, a spokesman for Fiat Chrysler.
Gordon Trowbridge, a spokesman for the NHTSA, declined to comment beyond the document.