Four fire engines and around 25 firefighters were called to a fire at a community library on Woodgrange Road in Forest Gate.
A small part of the roof was destroyed by fire. Around 30 members of staff and the public evacuated the building. Thankfully no injuries are reported.
Fire investigators believe the cause of the fire was accidental and due to the unsafe disposal of smoking materials.
A London Fire Brigade spokesperson said: "If you smoke it is vitally important you stub it right out, preferably in an ashtray.
"Always ensure your cigarette is completely out when you’ve finished smoking it. If you don’t, you risk causing a fire.
"Firefighters recommend that you have a look at our online Home Fire Safety Checker to make sure there are no hidden hazards in your home.
"The online tool will ask you a series of questions that will help us work out the level of risk in your home, or the home of someone you care for. It only takes a few minutes to get tailored advice to keep yourself and loved ones safe from fire.”
Control Officers took the first of nine calls at 1705 and mobilised fire crews from Stratford, Leytonstone, East Ham and Leyton fire stations to the scene. The fire was extinguished by 1806.