There were fires in two derelict buildings on Sunday (June 15).
The first took place just after 5pm at an abandoned care home, Sherd Lodge, in Sherd Close while the second occurred at 10pm at the former Venue 27 nightclub in Upper George Street.
Police are regarding the Sherd Close incident as suspicious and have arrested four juveniles. They have been released on bail pending further investigations.
Concerned members of the public made 24 calls to the emergency services about the blaze.
A fire service spokesman said: “Two crews from Luton arrived within minutes to discover an area 40m by 50m alight in a two-storey derelict building.
“The fire had started on the first floor and spread to the roof.
“Two further appliances from Dunstable and Stopsley were sent to assist as well as an aerial platform from Luton.
“Firefighters used three main jets and 11 breathing apparatus. It was declared under control at 7.27pm.”
Crews from Luton, Dunstable, Stopsley and Leighton Buzzard tackled the nightclub blaze and positive pressure ventilation was used to help clear smoke from the building.