Honolulu firefighters battled a pair of dramatic fires on the University of Hawaii lower campus and in Kailua on Thursday.

Around 6:45 p.m. firefighters were called to UH-Manoa’s lower campus, where fire had engulfed a Hawaiian Electric Co. substation on Kalele Road near Les Murakami Stadium.

An HFD spokeswoman indicated that the fire was caused by a blown transformer.

Witnesses reported hearing a loud explosion prior to the fire. Thick, black smoke was visible from miles away.

The fire was brought under control by 8:06 p.m., and fully extinguished by 8:23 p.m.

The fire resulted in a power outage that affected more than 3,300 HECO customers in the Diamond Head, Kapahulu, Lower Punchbowl, Makiki, Manoa, Nuuanu, Punchbowl and St. Louis areas.

Electrical service to all but portions of the UH- Manoa campus was restored by 8:40 p.m., HECO said.

Earlier in the day a blaze in Maunawili caused an estimated $1.8 million in damage to a vacant two-story residence on Maleko Street.

The fire was reported at 3:15 a.m., and the Honolulu Fire Department responded with nine units staffed by 34 personnel.

Firefighters brought the blaze under control at 6:09 a.m. and had it fully extinguished by 1 p.m.

HECO crews also were called to secure power to the building.

The Kailua structure, located within a cul-de-sac, was unoccupied at the time of the fire, and no injuries were reported.

According to online records, the home was built in 1975 and is 6,866 square feet with five bedrooms and 5-1/2 bathrooms.

Damage was estimated at $1.75 million to the structure and $50,000 to its contents.

The cause of that fire is still under investigation.