Officers raided several addresses in Tameside after receiving information from the public.
A 31-year-old man from Hyde, along with three men from Denton, aged 36, 22 and 24, were arrested on suspicion of robbery, police said.
The paintings were stolen from a house in Cheadle Hulme in May.
Art collector Ivan Aird was tied up and his wife and two-year-old daughter threatened during the robbery at their home.
Five artworks were taken, together with Lowry's palette and brushes.
The most valuable works are the Viaduct, at about £700,000 and The Tanker Entering The Tyne, which is worth between £500,000 and £600,000.
The others are pencil sketches - The Bridge at Ringley and The Street Market.
The value of the palette and paintbrushes is not known, because they are said to be so unique.
Det Con Chris Barnes said: "We have had a number of people come forward, both as a result of the media appeals and the recent Crimewatch appeal.
"A £70,000 reward remains available to anyone who provides information leading to the recovery and return of these paintings."
The raids were carried out in Audenshaw, Denton, Houghton Green, Hyde and Gorton.
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