They were found in a property in Sycamore Avenue, where some residents were woken in the early hours to find an Army bomb disposal unit truck outside.
A 69-year-old man has been arrested. It is believed the items, which were taken to a remote area of Scammonden before being blown up by bomb disposal experts, may have been homemade fireworks.
Residents in Sycamore Avenue said they were shocked by what happened. One said: “I heard it was a man who worked for a chemical company when he was younger and who had been making some pretty big fireworks. Strange to think they were just yards away from where we live.”
And another said: “At first I didn’t have a clue what was going on. I’d woken up early and looked out to see this big bomb disposal truck. Then it just drove off with its lights flashing. I didn’t know what to think.”
Up to six explosions were heard across the Colne Valley and Holme Valley as the controlled explosions were carried out early on Saturday.
A police spokesman said: “Officers searched a property in the Golcar area in connection with an ongoing police enquiry. During searches of the property, a number of potentially explosive substances were identified.
“The Army’s Bomb Disposal Unit attended to assess material and arranged for its safe removal. A controlled explosion was later carried out to dispose of the items.
“A 69-year-old local man has been arrested on suspicion of explosives offences and has been released on bail. Enquiries are ongoing.”
The explosions could be heard for miles around, with many people woken between 4am and 6am. People took to social media to try to establish what had happened.
One resident in Meltham tweeted that vibrations had been “felt through the floor. First thought earthquake, second explosion.” Another reported six “extremely loud bangs” heard from the edge of the moors two miles outside Marsden.
Others thought it was a sonic boom from an aircraft – or that aliens had landed.
Examiner reporter Joanne Douglas, of Slaithwaite, tweeted: “Anyone in Colne Valley area hear a series of loud bangs about 4.45am? Sounded like bombs going off.”
A police spokesman added: “We recognise that local residents may have concerns as a result of this activity but we would like to reassure them that public safety has remained the priority of the investigating officers at all times.
“Precautionary measures were taken at the earliest opportunity to ensure the property presents no risk to the local community.
“We are grateful for the patience and cooperation of local residents during this time.”