Smoke and flames can be seen shooting from a fire at a seniors' complex in Delta, B.C. (Tennille Evelyn/CBC)

Fire crews spent most of Friday evening working to put out a massive blaze at a seniors' complex in Delta, B.C., south of Vancouver.

It took crews more than three hours to get a handle on the fire in the two-storey, wood-frame building at 4603 Evergreen Lane.

Smoke from the blaze was so thick that officials evacuated the entire city block for several hours, and one witness estimated the flames were 20 metres high.

It appears all of the building's residents, some of who are in their 80s and 90s, managed to escape.

It's not clear how badly the building was damaged, but it appears much of the second floor was destroyed.

The cause of the fire has not been determined, but several witnesses told CBC News they thought the fire started in or near the elevator.

"We could smell smoke earlier on, before the fire actually started, and we ran down to look but couldn't find nothing," said resident Sydney Mason.

Patricia Roberts, who lives in a unit in the area where the fire was most intense, said "the flames were erupting from next to the elevator."

"I'm very surprised," she said. "I've lived there a long time and never seen this. I'm just wondering when I'll get back in again."

The building's residents were taken to a nearby community centre. It was not clear when exactly they would be allowed to go back to their homes, but one official said it likely wouldn't be until next week.