RANCHO CUCAMONGA  (CBSLA.com) —  Authorities said a Montclair woman accidentally rolled a vehicle over her 3-month-old girl Sunday, causing the child’s death.

Officials said the victim’s family was at a fast-food restaurant for lunch just before noon in the 11200 block of Fourth Street in Rancho Cucamonga. The victim’s father had gone inside the eatery to place their order while the mother was securing the vehicle and getting her children out.

READ MORE: 4 Arrests Made In Connection With Lakewood Flash Mob Burglary Of Home Depot

A preliminary investigation revealed the family was using a borrowed vehicle and the mother was unfamiliar with its operation. She believed she had turned it off and was in the process of unloading her infant daughter and 3-year-old son.

After removing the infant from her car seat, the mother realized the vehicle was still running. She walked around to the driver’s side door still holding her baby. She said she reached in to turn the vehicle off but somehow it began rolling backward. The woman tried to apply the brakes and in the process lost hold of her daughter.

Officials said baby fell and was struck as the vehicle rolled backward.

The baby was transported via ambulance to the San Antonio Community Hospital in Upland, where she was pronounced dead.

READ MORE: Flyers Containing Hate Speech Related To Jewish People Distributed To Beverly Hills Homes

The mother was uninjured.

Officials described her as “extremely upset … but cooperative.”

She was released from the scene.

Members of the Rancho Cucamonga accident investigators are working on details of the case.

Authorities said at this time, alcohol or improper driving are not believed to be contributing factors.

MORE NEWS: Virgil Abloh, Louis Vuitton Artistic Director And Off-White Founder, Dies Of Cancer At 41

Anyone who may have witnessed the accident or who might have additional information pertaining to the case is asked to contact investigators at (909) 477-2800 or (909) 477-2817.