ELKHART, Ind. (AP) — A northern Indiana fire department says the cause of a fire that destroyed a recreational vehicle plant will remain undetermined.

Elkhart Fire Department Inspector Aaron Gerber said Monday that officials have finished their investigation of the March 12 fire at the Forest River plant and “no other indications were found at the scene that would aid in determining the fire cause.”

The fire cause the plant’s roof and walls to collapse and produced smoke that could be seen from miles away.

Five or six employees were inside the plant when the fire started. There were no injuries.

The plant produced Forest River’s Vibe brand of travel trailers.