A flare that attracted a coastguard and lifeboat search in Aberdeen was thought to have been set off inland.
Coastguard teams were tasked with searching the area around Nigg Bay last night after a red flare was sighted in the sky.
They received the call just before 8.50pm and spent about two hours searching Aberdeen harbour and approaches into the city.
Nothing was found and crews were stood down at about 10.30pm.
It is understood that the incident is being treated as a hoax.
Rescue teams from Cruden Bay and Stonehaven were also called out to help.
A coastguard spokesman said: “The area around Aberdeen was thoroughly searched and nothing was found.
“That has left us with the possibility that someone has set off the flare inland.”
Police confirmed that they were investigating the incident.
A spokesman said: “Around 8.45pm on Thursday, 18 February, 2021, officers were called to the Aberdeen harbour area following a report of a possible distress flare being seen.
“Together with HM Coastguard, a significant search was conducted but no vessels or individuals were traced and inquiries are ongoing.”