Residents at an apartment building in Cambridge were forced from their homes early Tuesday morning after a fire broke out in one of the units.

Crews were called to 46 Grantham Avenue around 5:30 a.m., but fortunately everyone had already exited the building after being alerted by the building’s alarms.

No one was injured, but one person was taken to hospital for possible smoke inhalation.

Fire officials say the flames were caused by careless smoking in one of the five units in the building.

Cambridge Fire Platoon Chief Martin Mills says “The woman was smoking in bed, yeah, a lot of damage to that area.”

The situation could have been a lot worse though, as oxygen tanks could be seen in the building near where the fire started.

A sign on the door of the apartment where the fire originated also appears to indicate oxygen is in use.

Mills adds “They had working interconnected smoke alarms that the occupants did hear, which definitely helped them in getting out of the house.”

Neighbour Len Little says he saw the flames “I just seen a house on fire and I came out. My first instinct was to go rescue the lady downstairs and the dog.”

While exterior damage is minimal, the area where the fire started is burned beyond recognition. Damage is estimated at over $50,000.

Mills says there is a “little bit of structural damage, but mostly contents damage.”

The Red Cross is helping some of the residents displaced by the fire and it’s unclear when they’ll be able to return to their homes.