A wooden gazebo at the back of a pub in rural Fylde was badly damaged in a suspected arson attack.
Four fire engines and crews - two from South Shore in Blackpool and one each from Wesham and Lytham - were called to The Birley Arms Hotel and Gastro Pub in Bryning Lane, Warton, at 8.22pm yesterday.
Firefighters, some wearing breathing masks, used water jets to extinguish the flames, a spokesman for the Lancashire Fire and Rescue Service (LFRS) said this morning.
Nobody was hurt, and firefighters were at the pub, which also has 16 en-suite bedrooms, for around 90 minutes.
Director Felix Santoni said around 75 guests had to be evacuated, and said CCTV cameras showed two boys, aged around 14, approaching the pub shortly before the fire broke out.
One was walking, and the other was on a bike, he said.
The arsonists are believed to have set fire to chairs being stored inside the gazebo before leaving the scene, a spokesman for Lancashire Police said.
Punters spotted the flames and dialled 999, he added.
An investigation is now underway, and information can be reported to officers by calling 101, quoting log number 1456 of Monday, October 1.