NEW YORK: A US flag on the first steel column for the Freedom Tower at the World Trade Centre site was removed - after red-faced builders realised the stars and stripes were on the wrong sides.

The Port Authority of New York removed the flag on the 31ft column after journalists questioned the display, which had the 50 stars on the right side instead of the left.

Federal flag code requires that, whether displayed horizontally or vertically, the blue field displaying 50 stars is always on the left side to the viewer.

A new flag will be put on the column, which was one of two raised in a ceremony on Tuesday.

A third column - covered with signatures of New Yorkers, September 11 victims' relatives and pictures of some firefighters killed in the 2001 attack - will be installed in the coming days.

The 1776ft tower is being built to replace the destroyed twin towers.