That's a problem if an aeroplane spears into soft ground. The Crater fills up with water and makes it dangerous to recover the crew's remains. Sometimes it is impossible to collect everything so once a reasonable amount is recovered then the operation stops and the hole is bulldozed over.
Used to be a joke about Chinese aviation in the 90s.
'If a Chinese airliner crashes and there are no foreigners on board then they just bulldoze over the hole.'