It is proven in a number of hadeeths that the Prophet (blessings and peace of Allah be upon him) said that the one who dies by drowning, or because of the plague or a stomach disease (diarrhoea) is a martyr. So the one who dies of the plague is a martyr, the one who dies of a stomach disease is a martyr, the one who drowns is a martyr, the one who is crushed by a falling wall is a martyr, the one who is killed for the sake of Allah is a martyr, the one who dies for the sake of Allah is a martyr, and there are a number of others who are martyrs.
This is by the grace of Allah, so that this ummah will have an advantage in terms of great reward, but the best of them are those who are martyred for the sake of Allah, who are killed for the sake of Allah. They are the best, and they are not to be washed (ghusl), and the funeral prayer is not to be offered for them, for they are alive with their Lord and given provision. Martyrs other than those who were martyred for the sake of Allah, such as those who died of a stomach disease or the plague, or those who were killed by falling walls or drowned, are to be washed and the funeral prayer is to be offered for them. Included with them are those who die in vehicle rollovers and car crashes; they are likened to the one who is crushed beneath a falling wall, and there is the hope that they will have the status of martyrdom, but they are to be washed and the funeral prayer is to offered for them, as is done for those who die of stomach diseases or drowning. End quote.
Shaykh ‘Abd al-‘Azeez ibn Baaz (may Allah have mercy on him)
Fataawa Noor ‘ala al-Darb, 3/1426
For more information please see the answer to question no. 45669.
And Allah knows best.