The building was the main headquarters for the independent music distributor PIAS and held the stock of over 150 record labels, including XL Recordings, Beggars, Domino and Wall Of Sound.
An official PIAS statement read: "There was a fire last night at the SonyDADC warehouse which services the physical distribution for PIAS in the UK and Ireland.
"PIAS is working closely with SonyDADC who are implementing their emergency plans. PIAS's UK offices in London and all other areas of our business are unaffected. More information will be communicated shortly to all our labels and partners."
One affected label, Memphis Industries, wrote on Twitter: "So all the stock we got left is sitting in our office. Devastated is the word. Thoughts go out to all other PIAS labels too."
Record label Angular told The Quietus that its entire stock had been destroyed in the fire.
Other labels, including Masters of Cinema, Buzzin Fly and Full Time Hobby, have also confirmed via Twitter that all their stock had been lost.
Singer-songwriter Patrick Wolf said: "Today my love goes to PIAS and all the affected labels, I lost my own label 'BCM' stock too, the bachelor album and all the 7" singles RIP x"
Alex Kapranos, whose band Franz Ferdinand are signed to indie label Domino, added: "Thoughts go out to all the labels who have lost their stock in PIAS fire."
Beggars Group chairman Martin Mills told MusicWeek that his labels had lost stock in the "horrible, horrible" incident for the indie sector, but said that his and other larger labels would be less affected than smaller ones, because they also held stock elsewhere.
Hannah Morgan, aka fionchadd - the violinist of Rumour Cubes - has launched the #piasfundraiser tag on Twitter and has amassed support for future fundraising efforts to back independent labels.