The destruction of the US Securities and Exchange Commission's field office in New York City is likely to hinder, but not halt, major investigations by the US's top market regulator, said former SEC officials and lawyers.

Investigations such as the inquiry into initial public offerings involving the US unit of Credit Suisse Group would be set back by the loss of any documents stored at the SEC's Northeast Regional Office, they said.

The office was located in 7 World Trade Centre, which collapsed on Tuesday, along with the neighbouring twin towers that were hit by hijacked jetliners.

SEC staff members were evacuated safely before their 47-storey building came down in a cloud of dust and flames, said an SEC spokesman.