It is believed a fire at a Blackpool Wetherspoons was caused by people throwing a full basket of wood onto a log burner in the pub.
A full evacuation of the Velvet Coaster pub on the Promenade was carried out shortly after midnight on Saturday after staff discovered the roof was on fire.
A spokesman for Wetherspoons said: "It was discovered that a table of customers sat in the booth had thrown on a full basket of wood into the fire.
"This was confirmed by the fire brigade that this had been the cause for the fire lifting through the chimney stem and setting alight to the fan on the roof."
It was initially reported by the fire service that a fire had taken place at a hotel on the Promenade not a pub.
A spokesman for Lancashire Fire and Rescue said: "Four engines from Blackpool, South Shore, St Annes and the aerial ladder platform attended a fire involving a log burner at roof level in a pub on the promenade.
"Firefighters used one hose reel and a triple extension ladder to bring the fire under control. Crews were at the scene for fifty minutes."
The Velvet Coaster is one of the biggest Wetherspoons in the country and opened in 2015.