Senior managers moved the operations of the bank to emergency headquarters on the north-west edge of Paris and distributed other functions across the world, in an instant demonstration of what new technology can do. They claimed there was little disruption to services. Bank staff who turned up in the morning, for want of other instructions, showed more emotion.
Some lamented the loss of the spectacular and recently restored interior of the building, which dated from the turn of the century. Others feared that the fire would prove the death knell for the bank, which registered a tiny profit last year after being saved from bankruptcy in 1994 following a series of disastrous investment decisions and losses of 12bn francs (pounds 1.5bn). What had Credit Lyonnais done so wrong, a young secretary asked, to have had yet another misfortune visited on it?
Across the road from the northern facade of the bank, which suffered least from the fire, a shifting crowd of people, many of them elderly and most of them worried, pressed around a white Credit Lyonnais van. This van, familiar to almost everyone in France from its ubiquitous presence at the Tour de France cycle race, was labelled "Reception" and plastered over with stickers advertising an emergency telephone number.
By afternoon, bank staff - all with badges showing their name and department - had given up working from inside the van and were out in the crowd, addressing queries from all comers. Many came from little old ladies, with grey hair, glasses and sensible shoes, terrified their life's savings had gone up in smoke with the bank. One or two, close to tears and shielding their faces from the television cameras, were even resigned to that eventuality, as though their life-long fear - the collapse of the bank - had finally come about.
A cynical woman in middle age said she did not believe a word of the patient reassurance a uniformed member of staff had just given her.
Reflecting the widespread popular disdain in France for the government's Fr50bn bail-out of Credit Lyonnais, she said that the fire would be a pretext for winding up the bank and cheating the investors.
One man was concerned about his safe deposit box and asked why the police had prevented him from entering the building to recover it.
Luc Durieux, from the communications department, explained gently that no one was being allowed in for safety reasons, that elaborate security precautions were in place and that he would be informed as soon as access was possible.
Shortly before, the head of the bank, Jean Peyrelevade, issued a statement saying the fire had not penetrated the first basement which housed the strong room and that water was not believed to have penetrated any of the 9,000 deposit boxes.
Mr Peyrelevade also expressed the plaintive hope that this latest disaster might make people think more kindly of the bank in future.