Messenger of Allah ﷺ said, "Five are regarded as martyrs: They are those who die because of plague, Abdominal disease, drowning or a falling building etc., and the martyrs in Allah's Cause." (Using translation from Bukhārī 2829)  

أَنَّ رَسُولَ اللهِ ﷺ قَالَ «الشُّهَدَاءُ خَمْسَةٌ الْمَطْعُونُ وَالْمَبْطُونُ وَالْغَرِقُ وَصَاحِبُ الْهَدْمِ وَالشَّهِيدُ فِي سَبِيلِ اللهِ»