Hawaii County firefighters are investigating how recycled bales of cardboard, paper and plastics caught on fire in several locations at a Keaau warehouse, jeopardizing the 36,000-square-foot building.

About half of the recycling warehouse on Kipimana Street in the Shipman Industrial Park was full of compressed bales of recyclable materials stacked 16 feet high that were burning in several areas of the warehouse Monday morning, firefighters said.

The first firefighters arrived at 1:13 a.m. and had the blaze under control by 5 a.m. It was extinguished at 6:30 a.m.

As crews battled the fires, the county brought in a front loader and the owner of the recycling company provided a second one to remove smoldering bales out of the structure, where firefighters extinguished them.

In some cases, the material caught fire again once it was exposed to air outside the building, firefighters said.

The recycling company also used a skid steer and mini excavator to take material outside.

The efforts combined to save the warehouse “from substantial damage,” the fire department said.

There was no estimate on the damage immediately available.