Workers were told to go back to desks after first attack
Survivors are claiming World Trade Centre fire safety staff told people to return to their desks after the first plane attack.
Some of those employed in tower two say they heard an announcement saying the building was secure as they evacuated it.
Officials of the Port Authority of New York and New Jersey, which runs the World Trade Centre, have declined to discuss the claims.
Nancy Cassidy, who worked on the 80th floor, fled her office after a jet smashed into the neighbouring tower, sending fireballs flying past her window.
She was making her way down a stairwell with colleagues of the Mizuho Capital Markets trading company and thousands of others when she says she heard the announcement.
Ms Cassidy said the announcement said: "Building One is in a state of emergency; Building Two is secure. You're fine, you can return to your work stations.'"
Ms Cassidy, who ignored the announcement, said: "It could be that because of that announcement, some people from my company went back upstairs and now may be gone."
