Two more people are now under arrest after a bullet was fired through the door of a house in Ribbleton.
A single shot from a shotgun had been fired through the door of a house in Browning Road shortly before 2am on Tuesday.
A 38-year-old woman and 25-year-old man, both from Preston, were arrested on Tuesday on suspicion of possession of a firearm with intent to cause fear of violence.
The duo join two others in police custody - a 30-year-old man and 20-year-old man, from Preston, who were arrested on suspicion of possession of a firearm with intent to cause fear of violence.
Detective chief inspector Richard McCutcheon of Lancashire Constabulary said: “Although we have arrested people in connection with our investigation, our enquiries are still on-going and I would continue to appeal to anyone who saw or heard anything suspicious or who has information which could assist to get in touch.
“I would like to reassure the community that this incident was not directed at the general public and appears to be a targeted attack.”
A vehicle believed to have been used in the incident has been recovered.
Anyone with information should contact police on 101 quoting log 0070 of October 23 or independent charity Crimestoppers on 0800 555 111.