Toshiba Corp. late Monday emerged victorious in the frenzied auction for Westinghouse Electric Co., but analysts caution that the Japanese company could find it hard to justify the $5 billion purchase price it has reportedly agreed to pay.

Terms of the deal were not disclosed, but multiple industry sources said Tuesday that the Japanese company had won the N.M. Rothschild & Sons Ltd.-run auction with a bid of more than $5 billion for the nuclear power plant builder.