The froth appeared shortly after disastrous tremors from a 7.3 magnitude quake shook the city of Fukuoka on Friday. Twitter users posted photos of the snow-like foam sheet and wondered what caused it.

http://twitter.com/R0KlA/status/721026033135190016?ref_src=twsrc%5Etfw

The unexplained phenomenon affected the downtown Tenjin and Imaizumi areas of Fukuoka, according to reports.

http://twitter.com/The_takafumi/status/721021819390533632/photo/1?ref_src=twsrc%5Etfw

Some speculated that it may be the result of a burst underground pipe caused by the earthquake. Others suggested it could have been common firefighting foam, although no fire trucks could be seen anywhere in the photos.

http://twitter.com/_xPIYOx_/status/721027566815956993?ref_src=twsrc%5Etfw

http://twitter.com/yuuking1015/status/721038259401261056?ref_src=twsrc%5Etfw

One witness however believes he has solved the mystery… claiming it was caused by a burst fire sprinkler in front of a friend’s store.

今泉にある友達の店の前が、スプリンクラー破裂で泡まみれになっとる。皆さん、大丈夫でしょうか？#地震 pic.twitter.com/1HkxGJHYFY

— 岩本壮一郎　一般社団法人日本金融経済教育機構　代表理事 (@ilinkCEO_NOW) April 15, 2016

READ MORE: Over 40 killed, 90,000 evacuated as Japan hit by 2 powerful quakes & devastating landslides (PHOTOS)

The death toll from Japan’s two earthquakes has reached over 40 while 90,000 people have been evacuated from their homes.

Over 200 aftershocks have hit Japan following the initial Thursday tremor of 6.5-magnitude, which hit the city of Kumamoto on the island of Kyushu.