Coastguard teams carried out a sweep of the shoreline after flares were set off in a village.
The latest incident in Horden follows on from a series of similar reports over the last week.
Just after 4.30pm yesterday, the Coastguard received a call to say there had been more sightings of flares being set off.
Its teams in Hartlepool and Seaham carried out a check and with nothing found, they were stood down and returned to station.
A spokesman the service said: "Please remember flares should only be set off in an emergency and not to be used for your enjoyment."
On Wednesday afternoon, members of the Coastguard team in Hartlepool teamed up with Durham Constabulary to carry out checks after flares were let off in the village.
New and spend flares were recovered from the rear of Sixth Street.
Checks were carried out to ensure no vessels were in trouble.
In the wake of that and other incidents, the service has issued guidance that flares contain explosives and once they are past their expiry date, they must be disposed of carefully.
It has said it is illegal to dump them a sea or on land and to let them off in anything other than an emergency.