Tosefta for Nazir 65:9

It is the same whether one finds three corpses, or whether one finds three sepulchers, or whether one finds a sepulcher and a cleft grave and a hastily dug grave [at the same time], or whether one found ten and they do not have between four and eight cubits in between them: They all are subject to [the laws regarding the impurity of the] "surrounding earth," but they are subject to [the laws regarding the impurity of] a "graveyard site" (i.e., a cemetery) (see Mishnah Oholot 16:3), the words of Rabbi Shimon. And the Sages say, one looks at the middle ones as if they were not there, and the outer ones join together from four to eight cubits. [If] he found a [corpse's] head next to its legs, it is not subject to [the laws of] "surrounding earth," and it is not subject to [the laws of] a "graveyard site." The head of this one next to the body of that one, and the head of that one next to the body of this one: They are subject to [the laws of] "surrounding earth," but they are not subject to [the laws of] a "graveyard site." And that which is missing is subject neither to "surrounding earth" nor to a "graveyard site." And what does "missing" mean? Anything that would cause someone to die if it was removed when he was alive. [If] he found two [corpses] for the first time, and one [more] is known [to exist], they are subject to "surrounding earth," but they are not subject to a "graveyard site." It so happened with Rabbi Yeshevav, that he inspected and found two for the first time, and one was known. He made (i.e., designated) for them [an area of] "surrounding earth," [and] he made for them [an area of] a "graveyard site." When he came to the place of Rabbi Akiva, he said, "All your work was in vain. You would have had to inspect every known burial site in the Land of Israel (i.e., according to your logic). They only ruled regarding one who finds three [corpses] for the first time."

It is the same whether one finds three corpses, or whether one finds three sepulchers, or whether one finds a sepulcher and a cleft grave and a hastily dug grave [at the same time], or whether one found ten and they do not have between four and eight cubits in between them: They all are subject to [the laws regarding the impurity of the] "surrounding earth," but they are subject to [the laws regarding the impurity of] a "graveyard site" (i.e., a cemetery) (see Mishnah Oholot 16:3), the words of Rabbi Shimon. And the Sages say, one looks at the middle ones as if they were not there, and the outer ones join together from four to eight cubits. [If] he found a [corpse's] head next to its legs, it is not subject to [the laws of] "surrounding earth," and it is not subject to [the laws of] a "graveyard site." The head of this one next to the body of that one, and the head of that one next to the body of this one: They are subject to [the laws of] "surrounding earth," but they are not subject to [the laws of] a "graveyard site." And that which is missing is subject neither to "surrounding earth" nor to a "graveyard site." And what does "missing" mean? Anything that would cause someone to die if it was removed when he was alive. [If] he found two [corpses] for the first time, and one [more] is known [to exist], they are subject to "surrounding earth," but they are not subject to a "graveyard site." It so happened with Rabbi Yeshevav, that he inspected and found two for the first time, and one was known. He made (i.e., designated) for them [an area of] "surrounding earth," [and] he made for them [an area of] a "graveyard site." When he came to the place of Rabbi Akiva, he said, "All your work was in vain. You would have had to inspect every known burial site in the Land of Israel (i.e., according to your logic). They only ruled regarding one who finds three [corpses] for the first time."