ARCADIA — A fire early Wednesday destroyed a cluster of vacant temporary housing units that have been erected outside the U.S. Forest Service Headquarters as the agency constructs a new building, authorities said.

The new building itself, in the 700 block of North Santa Anita Avenue, was not damaged by the fire, Arcadia Fire Department officials said.

Destroyed were “26 modular structures, placed together to form one structure,” Arcadia Fire Department Senior Management Analyst Yvonne Yeung said.

A dollar-value estimate of the loss was not available.

No injuries were reported as a result of the blaze, and the affected structure had been unoccupied, “for some time,” Yeung said.

A fire engine responded to a report of a strong odor of smoke about 12:40 Wednesday morning from a resident of the 600 block of Cornell Drive, officials said.

Additional firefighters from the Arcadia, Monrovia, Pasadena and South Pasadena fire departments were summoned to help once initial firefighters on-scene realized the source of the smoke was the nearby temporary structure, Yeung said.

“The fire was quite heavy,” Yeung said. “The structure was deemed unstable. Fire personnel were unable to make entry to the structure, so they used defensive tactics.”

The fire appeared accidental in nature, though further details on how it ignited were not available Wednesday morning.

PHOTOS courtesy of the Arcadia Fire Department