Rescuers struggle to access building in dense residential area.

Authorities believe candles used for lighting a likely cause of blaze.         

Firefighters say origin of fire is not immediately clear.

Kids' mother being treated in hospital, is 'extremely distressed'.

Milan mayor says blaze started in a room housing 2 female residents.

A group of young people 'seen running from the fire scene shortly after 4pm', says official.

Two children are in critical condition.

Videos on social media show landmark covered in flames, black smoke.

Inferno started at TNB substation room in complex, Fire and Rescue Dept says.