West Yorkshire Police said the incident, on Bull Green Roundabout in Halifax, is being treated as arson.
The attack involved a silver Volvo which was reversed into the front of the building, before the vehicle was deliberately set on fire around 2.30am on January 21.
According to an eyewitness, the building, which had been sold by property firm Walker Singleton in December, was vacant at the time of the incident.
Detective Inspector Sam Lindsay, of Calderdale District CID, said: “This was a serious incident with the potential for people living in neighbouring properties to come to real harm.
"Thankfully no-one was injured due to the quick actions of the occupants of the flat above. This is being treated as a targeted attack, with the same property also being the subject of a previous arson attack last month.
“We've extensive enquiries ongoing to identify those responsible.
"As part of this, we would ask anyone who was in the vicinity who has seen or heard anything suspicious or anyone with any other information that could assist our ongoing investigation to please contact Calderdale CID.”
Police also said there is no threat to the wider community.
A spokeswoman from the West Yorkshire Fire and Rescue Service said: "The fire happened on the ground floor only. Three crew attended the incident from Halifax, Illingworth, and Odsal, with the last crew leaving around 5am."
Information can be passed to CID or by calling 101, quoting crime reference 131200035693.