Ananova:

Fire investigators are due to examine the sprinkler system at the warehouse where up to four firefighters died.

Fire officers entered the warehouse in Atherstone On Stour, Warwickshire, on Saturday evening for the first time since Friday night's blaze to make an initial assessment.

Warwickshire Fire Service said one firefighter has been pronounced dead and three others are missing, feared dead.

A family friend named one of the missing firefighters as Ashley Stephens, 21, of Meadow Road, Alcester, Warwickshire.

A search and rescue team briefly entered the collapsed building after colleagues finished damping down.

The team spent just a few minutes inside the fire-ravaged vegetable packing warehouse, only managing to make it a few feet inside.

Police and fire officers are due to return to the scene, when they will be joined by structural engineers and the Health and Safety Executive.

The tactics firefighters used to tackle the blaze will be investigated, said Warwickshire's Chief Fire Officer, William Brown.

Prime Minister Gordon Brown led the tributes to those killed and missing, saying he was "shocked and saddened" by the news.

Police said the fire will be treated as suspicious until its cause was established and appealed for witnesses.