A Greenpeace protest in Vancouver aimed at an oil pipeline expansion project was blown slightly off course Tuesday.

Activists dropped a huge banner below the Lions Gate bridge reading "Save our coast, no tar sands pipelines" to protest a plan by Kinder Morgan to more than double the capacity of its existing pipeline from Alberta to Burnaby.

Two protesters were also suspended from the bridge to try to weigh down the banner, but the sheet acted as a giant sail in the wind and blew back under the bridge.

The banner was removed about 40 minutes later and no commercial vessel traffic under the bridge was affected, although vehicle traffic on the bridge was backed up during the protest.

Kinder Morgan says it wants to increase the capacity of its oil pipeline from the current 300,000 barrels a day to as much as 750,000 barrels.

Greenpeace and other opponents of the plan say that would boost tanker traffic and increase the risk of a major oil spill in Vancouver harbour or along the B.C. coast.