Hertfordshire chief constable Frank Whiteley remained hopeful last night that the "apocalyptic" blaze at Buncefield fuel depot could be under control as early as breakfast time today, with a start made to returning people to their homes later in the morning.
He was speaking after firefighters had been forced to halt work at the site amid fears of a potential explosion from one tank holding fuel thought to be "extremely volatile".
Fire service chief Roy Wilsher confirmed that operations had been halted mid-afternoon, saying: "Until we are absolutely sure what is in that tank, we have withdrawn our firefighters. The last thing we want is a human tragedy."
However Mr Wilsher said that while the withdrawal was "significant as far as the operation is concerned", it was a "temporary setback" and the "worst case scenario" would be that the fires would be allowed to burn themselves out.
Later the firefighting battle resumed after it was established that the tank was not as dangerous as first thought.
The situation was "still fluid and very dynamic", he said, with firefighters facing "unprecedented scales of complexity". But he predicted they would be back on site as shift changes were completed and various logistical issues resolved. "We're still hopeful the fire will be out by about breakfast time . . . I think we're going forward, and remaining in control, and that the situation will be resolved."
Some 150 firefighters had earlier put out the fires in 12 tanks in a smothering operation involving high-volume pumps using some 32,000 litres of water mixed with foam concentrate per minute.
"It looks like an apocalypse," Mr Wilsher said.