A reward has been offered after a business near Daventry was burnt out in a suspected arson attack.
Badby Lodge Farm, the base for Hybrid Bootcamp's UK operations, was hit by an arson attack in the early hours of January 3 this year.
Hybrid Bootcamp operates a retreat at the building, which has space for around 15 to 20 people, who stay at the centre for fitness and weight loss boot camps.
Owner Lee Andrew said: "We get people coming from all over the world - Israel, Dubai, all over. They come and spend a week here for the boot camp, where we can control the whole environment.
"The arson has taken out our UK operation. The camps we do in other countries are unaffected, but this was our UK base. It also happened at the start of January so I've missed out on that post-New Year rush. January has been our busy time of the year.
"Whoever did this must have been watching the property. Usually, there's always someone in the building, but that night we were all away.
"Whoever did it used a lot of accelerant say the police, so I think they must have had a van or other vehicle to transport it in.
"We have local staff that have been affected, and we used to take our clients out to local places like village pubs, so it's bad for the wider economy as well."
An anonymous person has now offered a reward for up to £20,000 for information leading to a conviction.
Northamptonshire Police say the fire was started at around 3.15am on January 3. Four engines were called to the scene.
Witnesses or anyone with information about this incident can contact Northamptonshire Police on 101.