San Jose Fire Capt. Reggie Williams says crews were putting out the fire to some trees and brush near an onramp to northbound Highway 85 when they discovered the body late Tuesday night.
Williams said the victim's burns were so severe that authorities could not determine whether it is a man or a woman.
Authorities say that the victim was likely homeless and may have been camping in the area as crews also found a mattress and a tent at the site.
Williams added that investigators are now trying to determine whether the fire started accidentally.