The condition of a 3-year-old girl critically hurt in a crash at a south London Costco is improving, police say.

Miah Bozek has been in hospital since the horrific crash on July 25 that killed her sisters Addison, 6, and newborn baby Rhiannon.

The update means both she and her mom, Danah McKinnon Bozek, are now listed in "good," condition.

McKinnon-Bozek, who was eight months pregnant, was at the Wellington Rd. big-box store around noon when a red Monte Carlo inexplicably reversed through the front doors.

McKinnon-Bozek had an emergency caesarean section following the crash. Baby Rhiannon was listed in critical condition for seven days before being pronounced dead on Friday.

Two other adults and the driver of the car were injured but have since been released from hospital.

Police are still investigating the cause of the crash and say it could still be several days before they complete that probe.

They have not released the name of the driver.