The stocks of several of the largest banks and brokerages plummeted Thursday on speculation that they had suffered substantial losses because of a sharp rally in the 30-year Treasury bond.

Investors feared companies with big bond trading operations had substantial short positions on the 30-year Treasury and were getting "killed" by the rally, said Andy Collins, an analyst at ING Barings.

Subscribe Now

Access to authoritative analysis and perspective and our data-driven report series.

14-Day Free Trial

No credit card required. Complete access to articles, breaking news and industry data.