Shaun Walmsley was sprung from custody by two armed men in February as he was getting into a cab with prison officers at Aintree University Hospital.
Merseyside Police have detained four people from Anfield - women aged 33 and 65, and men aged 38 and 66.
They are all being held on suspicion of assisting a person unlawfully at large and money laundering, police said.
After executing warrants in Anfield and Kinmel Bay in Conwy, officers also seized a "significant quantity of cash" and two vehicles, which will now be forensically examined.
Fourteen people have now been arrested in the investigation - the 10 people held previously have been released pending further inquiries.
Walmsley is one of four men serving life sentences for murdering Anthony Duffy in 2014.
Police have offered Â£20,000 of Walmsley's own money - seized by officers following his conviction - as a reward for information leading to his capture.
Detectives are appealing for information but have advised people not to approach Walmsley, who they describe as "highly dangerous".
Police hunting a "highly dangerous" convicted murderer who escaped custody in Liverpool have arrested four people.