An investigation is underway to determine the cause of a brush fire on the Big Island that scorched 25 to 30 acres of hard-to-get-to land on Sunday.

The fire was reported at 8:36 a.m. yesterday at the Hokukano Ranch, 2.5 miles above Greenwell Mountain Road.

The first unit from the Big Island fire department responded at 10:30 a.m. and firefighters continued to fight the blaze 9:20 a.m.

Ranch personnel are continuing to monitor the area for flareups, and the Hawaii Fire Department has asked for the public's help to report signs of smoke or burning activities over the next several days.