Ohalot, Chapter Sixteen, Mishnah Three
Our mishnah deals with how one would know whether he has come across an isolated dead body which he must bring to burial in a proper cemetary, or a burial ground, in which case it is forbidden
1) If one finds a corpse unexpectedly lying in its natural position, he may remove it along with the [blood-] saturated earth around it.
2) If he finds two, he may remove them along with the [blood-] saturated earth around it.
3) If he finds three, if there is a space of from four to eight cubits between the first and the last, that is, the space of a bier and its bearers, then it must be accounted a graveyard.
4) He must search [the ground] for twenty cubits from that point.
a) If he found [another corpse] at the end of those twenty cubits, he must search for a further twenty cubits from that place, since there are already grounds for belief [that this is a graveyard], in spite of the fact that if he had found this [lone grave] in the first case, he could have removed it with the [blood-] saturated earth around it.
Section one: The person finds a corpse buried in the ground in a place that wasn’t identified as a burial ground. He is allowed to move this corpse into a proper cemetery. He can assume that the body was put there temporarily until a more proper place was found. He should also take the blood-soaked ground around the corpse, for as we have seen, the blood has the status of the corpse and must be brought to burial.
Section two: The same is true if he finds two corpses. He still does not need to worry lest he has stumbled upon a burial ground.
Section three: However, if he finds three corpses and they are between four to eight cubits between each body, he must consider the land to be a burial ground, in which case it is forbidden to move the bodies.
Section four: He now must search the area for other bodies so that he can determine the size of the burial ground. He should search twenty cubits from the outer body on each side.
And if he finds another body he must continue to search twenty cubits from the furthest body. This is true despite the fact that had he found this body as a lone grave, he would not have had to search for other bodies in the area. Once it has been established that there might be a burial ground in the area, he must treat each body as evidence of such.