This article has been updated.
Lake County, Calif. -- A wildfire North East of Middletown consumed approximately 20 acres Monday afternoon.
Forward progress was halted before 2:30 p.m Monday, according to Cal Fire.
The fire is in the area of Jerusalem Grade Road near June Bug Drive and was identified as the 'Grade' fire by Cal Fire.
Cal Fire reports that as of four p.m., crews have achieved 50% containment.
As many as 20 structures were threatened and one structure had been found destroyed, Cal Fire said.
The fire was reported shortly after noon. Forward progress of the fire was stopped by ground and air crews.
The Lake County Sheriff's Office issued an evacuation advisory Monday afternoon during the fire to warn residents of the possiblity for evacuations.
In addition to three fire crews Calfire utilized four helicopters and had called upon two C-130 air tankers which were not utilized.
A total of 150 personnel are fighting the Grad fire including 20 fire engines, five water tenders, one volunteer company, three fire crews, four helicopters, five overhead personnel, five bulldozers and four air tankers.
Roads remain closed in the area as crews will be working through the night to mop-up hot spots.