Investigations into the cause of a warehouse blaze in Warwickshire that killed four firefighters could take weeks, police have said.
Officers said a fingertip search of the Atherstone-on-Stour plant had been hampered by the dangerous building.
Ken Lawrence, of Warwickshire Police, said the site's current state meant it was unsafe to work.
Police have revealed there were 50 people at the site of the blaze when the first fire crews arrived.
'Bit by bit'
Four crews were at the scene on Friday night within minutes of the alarm being raised by employees.
More than 100 officers are taking part in the investigation and plan to interview everyone who was at the scene.
Mr Lawrence said structural engineers were examining the plant and would dismantle the structure "bit by bit".
Crews are still carrying out a fingertip search of the building
He said the last thing they wanted was for anyone else to be killed or injured by working in the building.
Ian Reid, 44, died in hospital after his body was dragged from the burning warehouse.
The bodies of Darren Yates-Badley, 24, Ashley Stephens, 20, and 27-year-old John Averis were given a guard of honour when they were taken out of the wreckage on Tuesday night.
Police said they were treating the fire as suspicious.
Mr Lawrence said: "We are searching meticulously what is left of the building.
"It is a very slow process. It is probably going to take a few weeks. The building is now classed as very unsafe.
"There is always the possibility that we could find things that might indicate to us where the fire started or what might have started it.
"The last thing we want is an injury or fatality. That would be a disaster." he said.
He added that they had "an obligation" to the men's families to find out what happened.