Vancouver fire investigators have determined oily rags are to blame for a weekend highrise fire that began on a balcony.

"The fire investigators have completed their investigation and processed the evidence and concluded that the fire was caused by improperly stored linseed oil rags used for staining furniture," said Vancouver Fire Rescue Information Officer Jonathan Gormick.

Linseed oil is a natural oil that is used to restore furniture. Natural oils have a self-heating property.

The fire broke out at around 5 p.m. on Sunday.

Heavy smoke and flames could be seen shooting out of a 15th floor suite of the Pacific Avenue highrise.

"Fire damage was contained to the suite of origin. Other suites were affected by some smoke damage and there was a small number of displaced residents," Gormick added.

As linseed oil dries, it can heat up and reach the right temperature to combust, said Assistant Fire Chief Ray Bryant.

"In this case they were rolled up into a ball. When you do that with a self-heating oil, it can release the heat that is generated as the product starts to dry," said Bryant. "You’ll get temperatures from 4 to 500 degrees Fahrenheit within that rag at which time it will start to ignite. That is what happened in this case."

The process of heating and combusting can take up to three hours but in this case, the process was accelerated by the rags being left on the balcony in the hot sun.

Since 2016, Vancouver Fire has had 39 similar incidents of self-heating.

The fire department recommends safe storage of oily rags in a non-combustible covered container or drying them by laying them flat on a non-combustible surface and disposing of them when they have hardened.