Vancouver police and fire officials are investigating reports that a group of people was seen running away as fire engulfed the CP Railway trestle near the Oak Street Bridge in South Vancouver yesterday afternoon.

The investigation is one of several now underway following the spectacular fire during the Wednesday afternoon rush hour on the wooden Marpole Bridge, which crosses the Fraser River.

The blaze caused a temporary closure of the neighbouring Oak Street Bridge because the thick smoke reduced visibility for drivers.

CP Rail spokesman Ed Greenberg says the railway has two investigations of its own underway.

"We have CP police now investigating the cause and we also have CP engineering experts who are going to be conducting a full inspection of the structure to determine the extent of damage," said Greenberg.

Brian Godlonton, deputy chief of the fire department, says the creosote on the wooden structure made the fire burn hot and fast, but one piece of equipment saved the day.

"The fire boat was instrumental. Without that, the structure and the integrity wouldn't have allowed our firefighters to get off the shore to attack the fire," said Godlonton.

The railway says the bridge, which was built in 1902, was handling rail traffic just once a week and no trains were on the tracks during the fire.

Since the rail line closed 15 years ago, the inactive right of way for the railway line has become a popular dog walking spot, and sprouted community fruit and vegetable gardens along the route in other areas of the city.

However, after development negotiations with city officials failed, CP recently ordered all property along the Arbutus corridor, including community gardens, be removed by July 31 and said the line may reopen.

On mobile? Click here for a YouTube video of the fire from the Oak Street bridge

On mobile? Click here for a YouTube video of the fire from the Skytrain to Waterfront