The cabin where fugitive former law enforcement officer Christopher Jordan Dorner was holed up is on fire as authorities try to determine whether the murder suspect is dead or alive.

San Bernardino County Sheriff Department officials said officials are trying to determine Dorner's whereabouts. It's unclear whether police have been able to get into the cabin.

Law enforcement sources said "a tactical operation" was underway at the cabin but did not provide additional details. A spokeswoman for the Sheriff’s Department said gunfire was heard just before the fire began.

PHOTOS: Manhunt for ex-LAPD officer

A tall plume of smoke was rising from the area where the standoff occurred. Hundreds of law enforcement personnel swooped down on the site near Big Bear after the gun battles between Dorner and officers that broke out in the snow-covered mountains where the fugitive had been eluding a massive manhunt since his truck was found burning in the area late last week.

Law enforcement personnel in military-style gear and armed with high-powered weapons were involved in a tense standoff after Dorner took refuge in the cabin Tuesday afternoon.

One San Bernardino County sheriff's deputy died of his wounds after he and another deputy were wounded in an exchange of gunfire outside the cabin in which hundreds of rounds were fired, sources told The Times. The deputy was airlifted to Loma Linda University Medical Center, where he died of his wounds.