A reader sends in this report: "There are gigantic smoke plumes, about 20 sirens went by, and it looks like it could be an apartment building. There were large flames. My office is in the Samsung building at La Brea and Wilshire, and we can see it from here (5th floor) with obstructed views so I can't quite tell. There are copters above and Channel 2 seems to be doing some web coverage of it..."
UPDATE: Yes, it's an apartment building, reports Reuters. A three-story structure, no reports of injuries.