The robbery occurred outside Haslingden News in Manchester Road shortly after 8.05am today (September 13).
A crash-in-transit guard was approached by two men carrying a baseball bat and a machete as he was about to refill a cash machine.
The masked men then stole a cash box before fleeing from the scene in a black Volkswagen Golf with a third man.
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The vehicle was later found by police following a short pursuit in the West Yorkshire area.
Cash and weapons have been seized by officers but no arrests have been made
Det Insp Mark Saunders, of Lancashire Police, said: "We are appealing for information and are keen to speak to anyone who saw what happened.
"This includes a number of people on board a bus which had stopped close to the scene of the raid.
"The offenders will have been in the immediate area before the robbery. Did you see anyone acting suspiciously? If so, please contact us."
The guard was not injured during the incident.
Anyone with information can contact police on 101, quoting log number 0260 of September 13.
Alternatively, independent charity Crimestoppers can be contacted anonymously on 0800 555 111 or online at crimestoppers-uk.org.
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