Officers raided addresses in Downing Street, Callon Street, Nevett Street, New Hall Lane and Acreage Close this morning (December 8).
Suspected cocaine and a firearm were discovered inside an address in Longridge, police said.
A 31-year-old from Preston was subsequently arrested on suspicion of possession with intent to supply Class A drugs and possession of a firearm.
A 17-year-old boy was also arrested on suspicion of possession with intent to supply Class B drugs after a large amount of suspected cannabis was found within an address in Downing Street.
Other items seized during the raids included a large amount of cannabis, over £1,100 in cash, knives and a hammer.
The warrants were conducted as part of Operation Vanquish - a new initiative launched by Lancashire Police to tackle crime in the county.
Det Chief Insp Zoe Russo, from Preston Police, said: "Today is the just the start of action we have planned in Preston, South Ribble, Chorley and West Lancashire, as part of Operation Vanquish, which is our policing operation to crackdown on crime and anti-social behaviour to keep you and your local area safe.
"We are taking the fight to criminals and as a result, people will see an increase in police activity, which will include many more arrests. We know that normal, decent people are being affected by the actions of those involved in drugs, burglary and antisocial behaviour, and we are determined to tackle them.
"We need residents to continue to work with us to let us know who these people are and what they are involved in. Also, if you suspect that drugs are being circulated in your area, please continue to help us to help you by sharing what you know."
Police said more work was planned for the coming weeks, including more warrants, community engagement activity, traffic enforcement and crime prevention work.
DCI Russo added: "My message to criminals is clear; you are not welcome on our streets and we will find you, sooner rather than later. We will leave no stone unturned in our efforts to keep our communities safe."
Andrew Snowden, Lancashire's Police and Crime Commissioner said he was "fully committed to ensuring Lancashire Constabulary has the resources it needs".
He added: "Operation Vanquish has been launched as part of the Chief Constable's response to my priority of seeing more actions that robustly take the fight to criminals.
"Conducting big show of strength operations against county lines gangs and others is part of my priority to relentlessly disrupt and dismantle organised crime.
"We are sending the clear message to criminals and those exploiting vulnerable people that we know who they are, we'll put them behind bars, seize their assets and use the money from them to make our streets safer."
Anyone with any information which may assist officers in their pledge to combat crime can speak to a local officer, report information online at doitonline.lancashire.police.uk or call 101.
Alternatively, independent charity Crimestoppers can be contacted anonymously on 0800 555 111 or online at crimestoppers-uk.org.
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