LEWISTON — Investigators spent hours at the scene of a Lisbon Street house fire Friday, but by late in the day the cause of the blaze was still being probed.

The fire at 777 Lisbon St. rousted Bert and Louise Dubois from their single-family home just before midnight Thursday. The couple escaped without injury along with a pair of dogs.

Firefighters got the blaze knocked down within minutes. Lewiston Fire Inspector Paul Ouellette and City Electrician Gerry Caron were sent into the burned building to begin an investigation. By late Friday afternoon, no cause had been found.

The fire started in the area of a porch at the back of the house, Ouellette said. The flames caused extensive fire and heat damage to the first floor and smoke damage to the second floor.

Damage was estimated at $80,000.

The couple was unable to return to their home. Friends said the couple have lived in the house for more than 30 years.

“They are super nice people,” longtime friend Rose Wilson of Poland said. “They have lived there as long as I have know them. I tried to convince her to move out to Poland with me. But she’s a city girl and I’m a country girl.”

The investigation was expected to continue into the weekend.

Ouellette pointed out that although the Dubois’ dogs, Abby and Sammy, were credited with barking and waking up the occupants, they weren’t the only fire safety equipment in the house.

“They had working smoke alarms in the house as well,” Ouellette said.