An initial police raid took place at industrial premises on Rodley Lane in Bramley last Wednesday, and a man was arrested on suspicion of manufacturing firearms after several weapons were found.
A 67-year-old man, of Fallwood Marina, Pollard Lane, was subsequently charged and appeared at Leeds Magistrates Court on Friday last week. He was remanded in custody pending a hearing at Leeds Crown Court.
Officers then searched the marina this Saturday and arrested two more men, aged 71 and 64, on suspicion of firearms offences.
Five boats and two container units were searched and further weapons discovered.
The two men arrested were later released pending further enquiries.
Fallwood Marina provides moorings for craft using the Leeds and Liverpool Canal, as well as boat-building and refitting services.
The investigation is continuing and anyone with any information that could assist officers is asked to contact the Leeds District Serious Organised Crime Unit via 101 or call the independent charity Crimestoppers anonymously on 0800 555 111.