It was a huge blow for the Levin AP&I committee, who owned the building independently, as the stable block was used regularly by the Horowhenua Riding Club and an adult riding club.
Levin AP&I Showground manager Jo Roberts said it was devastating news before their 144th annual show early next year. They would need to have it replaced in time for the show.
"We are really disappointed. It is extremely well used and a community asset. It was never dormant," she said.
"It's very disappointing for our members...there will be a cost involved in replacing it."
The scene was cordoned off and remained under police guard. Fire investigators were due onsite this morning to determine to cause, before contractors were would begin to remove the iron.