Some 30 people, including children, were injured Wednesday night in an explosion during a Jewish festival bonfire in north London.
Videos recorded at the event showed a bonfire being lit, followed by a large explosion and a fireball engulfing the crowd standing near the fire.
Some witnesses said the explosion was sparked by mobile phones being thrown into the bonfire, a tradition for Lag BaOmer, an annual Jewish festive day.
However, Jewish website Yeshiva reported that "it appears that the explosion was caused by fuel and not the smartphone, although there definitely were multiple smartphones placed inside the pile to be burned".
Ten people are believed to have been hospitalized. Their conditions were not known immediately.