United Kingdom — Olaf Baars, deputy chief fire officer, said that in terms of resources deployed it has exceeded the scale of the 1992 Windsor Castle fire.
Mr Baars said however, he believed the fire, which is affecting 300 hectares of forest, would soon be contained.
Although smaller than other wildfires burning in the UK, it is the only one close to a built-up area, he added.
The fire is also burning close to the high-security Broadmoor Hospital.
Two teenagers have been bailed after they were arrested on suspicion of arson by police investigating the fire.
Thames Valley Police said the arrests of the boys, both 14, were “not necessarily linked” to the fires in the forest.
Earlier, Mr Baars told a press conference he hoped to double the capacity of water available for fire crews to use, by drawing from the lake at Sandhurst Military Academy.
He said: “We will be maintaining a presence here for weeks, but sometime next week it should turn to a much more routine presence.
“[But this has become] the largest fire that Berkshire has ever dealt with – it exceeded the resource demands of fighting the Windsor Castle fire in 1992.
About 200 personnel from seven county forces are continuing to tackle pockets of fires and dampen down hot-spots at Swinley Forest.
Evacuated families and businesses are waiting for news on when they can return to their properties.
The fire, which is burning close to the Devil’s Highway near Bracknell, started on Monday.
Fires have burning in Swinley Forest since Monday
Residents Kelly and Simone Hutchinson were given 10 minutes to leave their wooden home, along with their two young sons.
Mrs Hutchinson said: “We could see the smoke billowing over… it got worse and worse as the hours went on, then we were told to go.
“I panicked for seven of those 10 minutes and in the remaining three I packed photos and some kids clothes which I left at home anyway.” Crews ‘exhausted’
The family have been told unless there is considerable rain they will not be able to return home for the “foreseeable future”.
Nicole Targett, fire service spokeswoman, said tackling the fire was difficult because dry peat was burning underground.
“It can pop up at any moment,” she said.
“The only thing that would help us out is torrential rainfall for about a week without stopping so we are trying to do that through our hoses.”
She said firefighters were “coping incredibly well” despite being “exhausted”.
The Met Office has forecasted the area will have to wait until at least Saturday for rain.
Firefighters have been praised for their efforts in tackling the fire
A number of businesses in the area have been evacuated, including the outdoor activity attraction Go Ape.
Grant Stevens, site manager, said about 700 bookings worth about £20,000 have been made for Saturday.
“We’re still waiting day-by-day to hear if we can get back in,” he said.
It is not known how the earlier fires originally started.
The A3095 Crowthorne Road remains closed because of the fire, which has also affected the B3430 Nine Mile Ride between Crowthorne and the Coral Reef roundabout.
Conservationists said they are concerned about the impact of the fire on wildlife and plants.
The 2,600-acre (1,052-hectare) forest contains conifer pine trees that are managed as timber crop and the woodland is also part of a Special Protection Area (SPA) for three rare birds – Dartford warblers, woodlarks and nightjars.