WASHINGTON -- The Treasury Department is considering buying equity stakes in insurance companies, a sign of how the government's $700 billion rescue program could turn into a piggy bank for a range of beleaguered industries.

The availability of U.S. government cash in the middle of a global credit squeeze is drawing requests from insurance firms, auto makers, state governments and transit agencies. While Treasury intended for the program to apply broadly, the growing requests could put a strain on the $700 billion, a sum that...