Problem: In verses 31–32 it says the earth opened and swallowed Korah and his 250 rebellious associates. Yet verse 35 asserts that fire came from God and consumed Korah and his associates.
Solution: Some scholars have suggested that Korah was burned along with the 250 other rebels. However, no verse actually affirms this and other verses seem to deny it (noted below).
It seems better to understand it as follows: Korah, Dathan, and Abiram (v. 27) were swallowed by the earth, while at the same time (cf. 26:10) a fire from God consumed the 250 other rebels who offered incense in the tabernacle (cf. Ps. 106:17–18).