Firefighters spent several hours clearing the scene of a house fire in North Portland Thursday morning while the homeowners were on vacation.

Investigators were also trying to pinpoint the cause of the fire. It broke out just after 1 a.m., near North Fortune Avenue and North Houghton Street.

A neighbor told KGW that a woman and her son lived in the house and were on vacation in Reno, NV when the fire broke out.

"I called to tell her the news," said neighbor and close friend, Patrice Townsend.

Another neighbor called 9-1-1 after seeing smoke coming from the rooftop.

Firefighters believe the fire likely began in the walls of the second floor. Dispatchers said it was especially hard to fight the fire because it spread to the attic, where there are small spaces and flames were tough to get to.

No one was hurt, but a dog and two cats were still unaccounted for.

A neighbor took in two more dogs that made it out of the house safely.

The specific cause of the fire remains under investigation.