The new terminal building at Paris's main airport may have to be demolished entirely after a section of its roof collapsed early yesterday, killing four people and injuring another three.

The victims were buried under tonnes of twisted steel, broken concrete and shattered glass when a 30-metre (100ft) section of Terminal 2E snapped and fell on to a walkway leading to aircraft at Charles de Gaulle airport.

There was a fresh scare today as the building was evacuated after cracking noises were heard emanating from the roof.

Pierre Graff, the president of Aeroports de Paris (ADP), which runs the airport, told Le Parisien newspaper today: "If all the ring sections which comprise the terminal prove to be unsound, then we will have to demolish it all, of course. We will take no risk when it comes to safety."

When it was opened in June 2003, Terminal 2E was described as an architectural gem and it was a key part of French plans to turn Charles De Gaulle into Europe's foremost air hub.

Paul Andreu, the building's architect, is returning to Paris from Beijing today to help with the investigation. M Andreu, who has been working on a new national theatre in the Chinese capital, has said that he was "aghast" at the tragedy.

Two of the victims in Paris were Chinese. Wu Xin, 32 and Liu Jianfang, 30, employees of a Chinese trading company, had been travelling from Shanghai to Mexico via the French capital.

A third victim was an unnamed Czech woman, while the nationality of the fourth victim remained unknown.

The French authorities have revised down the number of dead from five to four, after sniffer dogs that appeared to locate two bodies under the rubble had in fact found only one.

About 50 rescue workers were sifting through the rubble at the scene today, but there was little expectation of finding other bodies, in spite of earlier reports that as many as six people may have been killed.

President Jacques Chirac has ordered an urgent judicial inquiry, while a second, technical enquiry was due to be set up today to discover how such a disaster could have occurred.

Airport managers said that passengers and staff had noticed cracks in the wall shortly before it collapsed at 6.57am on Sunday.

It emerged last night that instead of ordering passengers to leave, police had photographed the crack and taken urgent action only when another crack appeared. Minutes later, the building collapsed. One employee said: "I was about 50 metres away when it happened and I suddenly heard a crack, then a crash."

The three people injured were all policeman called to the scene, according to Michel Clerel, chief doctor of Aeroports de Paris (ADP), which runs the airport.

Airport staff said that the mostly likely causes were a design fault or a mistake during construction of the £500 million terminal last year.

The judicial investigation will focus on whether there was a fundamental flaw in the conception of the terminal, or whether shorts cuts or poor materials were used in its construction.

Trade unions warned a year ago that ADP and Air France - the terminal's main user - were rushing the completion of the building because of commercial concerns. The opening of the terminal had to be delayed for a week after it failed to pass a security check.

French left-wing newspapers linked the disaster to proposals for the privatisation of ADP. They said the authorities were under constant pressure to cut costs, and that the 400 different sub-contractors used in the building of the terminal would make it very difficult to trace responsibility for the accident.

The terminal had been handling six million passengers a year, but the plans for expansion to 10 million by the end of this year have been dealt a severe blow.

Airport authorities said flight disruption would be kept to a minimum while the work to make the terminal safe was going on, with most planes diverted to other terminals.