Bomb disposal experts blew up a Second World War relic after it washed up on a beach in St Annes.
The rusty metal device was initially feared to be a 70-year-old explosive but it was later identified as a smoke marker.
But experts warned the marine flare could still have posed a threat to local residents due to the chemicals used to make them.
A Royal Navy bomb squad was brought in to make the beach safe after the foot-long object was spotted washed up on the beach close to St Annes pier over the weekend.
The bomb disposal team first tried to detonate the device on Sunday night but their plans were foiled by the tide and fading light.
The team returned at 8.30am yesterday to finish the job, carrying out a controlled explosion to dispose of the flare.
The device was found 500 metres away from the Promenade and roughly level with St Annes pier.
It is thought the smoke marker could have washed up on the beach after the recent bad weather that caused localised flooding up and down the Fylde coast.
The Coastguard was informed of the suspicious object on Sunday afternoon and has urged members of the public to be wary of unusual items they spot on the beach.
Paul Parkes, watch manager for Liverpool Coastguard, said: “The device was a Second World War smoke marker.
“It was 12 inches long and looked like a bit of rusty metal.
“Those devices use phosphor to make smoke and that is not something you want people to come into contact with.
“If anybody finds anything on the beach that looks suspicious they should report it to the police or to the coastguard.”
Police confirmed they were made aware of the incident by the coastguard but had no involvement in yesterday’s detonation.