Up to 250 people were forced to flee their homes after four gas canisters blew up at the £360m SouthGate retail development site in Bath, yesterday evening.

A fire engulfed the building, which is still under construction, after a tar heater used for asphalting caught alight at about 5pm.

Up to 10 canisters remained in a potentially dangerous state overnight and people living in nine streets within a 150 metre exclusion zone were moved to safe havens.

It is thought the fire did not spread beyond the shell of the block, and did not affect other parts of the development.

Work on the 417,000 sq ft development began last year and it was hoped the first shops would begin to open as early as 2009.

Multi Development UK is the developer of the project.