The Daat Zkenim in his commentary on this pasuk mentions this. He says:
'וימותו לפני ה, “as a result they died before the Lord.” We find a dispute recorded in the Torat Kohanim concerning the meaning of this phrase. According to Rabbi Eliezer, they died outside the Tabernacle in an area that the Levites were permitted to enter; he bases himself on the wording in verse five, in which the Torah describes how their bodies were removed from the spot where they died. The Torah describes the sons of Elitzafan, an uncle of Aaron as performing this task, with the words: ויקרבו וישאם בכתנתם אל מחוץ למחנה, ”they approached and lifted them up by their tunics and carried them out of the camp as they had been instructed to do by Moses.” If that is so, why did the Torah write that they died “before the Lord,” i.e. on sacred ground, not accessible to the Levites? This is why Rabbi Akiva disagreed and said that they had actually died inside sacred ground, and that the sons of Elitzafan had to use a long iron spear in order to pull placing that spear in their mouths and dragging their bodies to less sacred ground before they could lift them up, as they were only Levites and not priests. This presents us with a different problem, as in that event the Tabernacle itself would have become ritually impure as it formed a tent over the bodies of Nadav and Avihu, and it would have required purification rites which would last seven days. The Torah does not, however, report that the service in the Tabernacle had been interrupted for that length of time. Our author concludes that the subject needs further study. [Since the ash of the red heifer for cleansing oneself from impurity caused through contact with a dead body was not yet available, this editor does not see where the problem is.]
Similary, the Rashbam writes:
At the time the heavenly fire emanated in order to consume the sacrificial meat on the altar in the courtyard of the Tabernacle, it consumed the two sons of Aaron on its way. This fire had meant to consume only the incense, but seeing that the sons of Aaron had been in its way it consumed them also and they died as a result.
And see the commentary of the Chizkuni:
In this instance, the heavenly fire did not stop there, but travelled beyond the boundary of the Sanctuary to the copper altar in front of the Sanctuary and consumed these two sons of Aaron there.
