Firefighters were called to a hairdressers at St George’s Shopping Centre in Preston after smoke set off an alarm system.
Two officers wearing breathing apparatus entered Top Cut Hair in Friargate at around 6.10am on Saturday and used thermal imaging cameras to search for a fire.
However, they were unable to detect the cause of the incident.
Andrew Stringer, St George’s Shopping Centre manager, said: “We received an alarm notification just after 6am, which automatically called the fire brigade out.
“It was in the ex-Regis hairdressers, Top Cut Hair on Friargate, not inside the centre.
“When they got there, there was smoke inside the unit.
“They cleared the smoke, but were unable to find the actual cause of the smoke itself, which is rather strange.
“There was no damage and nobody was hurt.
“The unit is trading as normal today and the situation is being monitored.”