A sharp drop in Zions Bancorp’s stock price touched off declines among regional-bank stocks on Thursday, as the bank added to the noise around bad credit deals on Wall Street by disclosing a $50 million loss on two commercial loans.

In what one analyst described as a “step on a rake,” Zions

ZION said it would take a $60 million provision for credit losses when it reports third-quarter results on Oct. 20. Provisions for credit losses represent money that banks set aside to cover bad loans.