Forensic investigations got underway on Saturday afternoon to determine the actual cause of the fire. Police are investigating it as a case of aggravated arson. This offence carries a maximum sentence of ten years imprisonment.
Senior Criminal Investigating Officer Kari Tolvanen said the police now had firm reason to believe the fire was not started accidentally.
Christer Ahlqvist, Chief Fire-fighter from the City of Helsinki Rescue Service told YLE TV News the blaze was probably started by lighter fuel. It spread quickly via the eaves of the building.
The blaze was at the same site as a melee on May Day night in which protestors set a large fire and pelted police and fire-fighters with bottles and other projectiles. Police say they cannot at this stage say if the blaze is linked to this earlier incident.
Smoke Sent Across the City The large plume of smoke which rose from the fire caused concern to ambulance staff at the scene. Many spectators had gathered near the blaze, viewing in some cases from the steps of the adjacent Parliament House building. Later police evacuated the nearby area for fear of toxic smoke inhalation. However no dangerous substances were uncovered. However old railway sleepers gave off toxic fumes thus prompting evacuation of the area. The city's major thoroughfare Mannerheimintie was closed to traffic for a time on Friday evening but was reopened later in the night. No Injuries From Blaze
No injuries were reported from the blaze. Several rescue and fire-fighting crews were on hand shortly after the fire began just before 8 pm.
Half an hour later the southern warehouse building was completely engulfed in flames. Most of the building's southern wing was destroyed. However, a portion of the structure due to be preserved was saved from the inferno.
Authorities took steps to prevent the fire from spreading from the warehouse area. The nearest buildings were the Kiasma Museum of Contemporary Art and the Sanoma publishing company headquarters.
The fire was brought under control late on Friday night.
Demolition of the nineteenth-century brick buildings was to begin on Monday morning to make way for a new music hall. Over the past decade or so they had become an informal cultural centre. There had been considerable controversy about their demolition.