Fire officials investigating a huge blaze at London's Camden market say they know "exactly where" it started.
Progress has been hampered by concerns about structural safety
London Fire Brigade said it had received witness statements pinpointing the seat of the fire, but police said it was too early to say how it began.
A more thorough investigation is due to start at about 1000 GMT on Monday once the structure has been made safe.
Some residents have returned to their homes after being ordered to leave when the fire took hold on Saturday evening.
Market owners said they feared more than 300 stallholders and staff could lose their jobs because of the fire.
Local traders have said most of Camden is "open for business", but police have advised that the main roads could be closed for up to four days.
Storage buildings for the market and the Hawley Arms pub were severely damaged, but no injuries were reported.
Some 100 firefighters tackled the blaze, which began about 1920 GMT.
Nigel Hall, of the London Fire Brigade, said: "We do know exactly where the fire started. We've got some witness statements already... taken from people.
The cause of the incident we won't know until our investigators have managed to get in there once the building has been made safe... Along with the police, we'll investigate the seat of the fire."
Six people, including three children spent the night at an emergency shelter in a nearby sports hall set up by Camden Council.
A Scotland Yard spokesman said: "Chalk Farm Road and parts of Camden High Street, as well as surrounding one-way streets, are expected to be closed for the next three or four days."
The closures are to allow structural engineers to assess the damage to buildings, including the Hawley Arms, a popular Camden pub which is frequented by celebrities including singer Amy Winehouse.
Landlady Ruth Charles-Ridler said she was "devastated".
"Everyone I've spoken to is in complete shock."
The markets area is a major tourist attraction attracting up to 300,000 visitors each weekend to its six open-air and indoor markets and vibrant mix of bars, clubs, shops and restaurants.
In a statement, the owners of Camden market said: "More than 300 people who run stalls in the markets may lose their livelihoods and we will be doing all we can to get them back running their businesses."
A spokeswoman for Camden Council said it would keep open a rest centre for evacuees at Talacre Sports Centre "as long as it is needed".
Evacuees are being advised to call the council's emergency line on 0207 974 4444 for the latest information on rehousing.
Train services passing through Camden Town on the North London line were suspended during the blaze, and the line remains partly closed due to scheduled engineering works on Sunday.
Network Rail said it would check if any damage was caused to the tracks by the fire.
Ken Livingstone, Mayor of London, said: "Our thoughts are with those people affected by the fire in Camden Market - one of the most thriving markets in London and of enormous importance for the economy of the local area and beyond."
Conservative mayoral candidate Boris Johnson said: "This will come as a terrible blow to their livelihoods and the area generally. My thoughts are with the traders, local residents and the emergency services who are, as usual, performing brilliantly under pressure."