European Central Bank:

This changed with the recent sovereign-debt crisis. The ECB always could, and through the late summer of 2011 did, purchase bonds issued by the weaker states even though it assumes, in doing so, the risk of a deteriorating balance sheet. ECB buying focused primarily on Spanish and Italian debt. Certain techniques can minimise the impact. Purchases of Italian bonds by the central bank, for example, were intended to dampen international speculation and strengthen portfolios in the private sector and also the central bank.

Please answer a question about this article. If the question is unanswerable, say "unanswerable". What risk is assumed when the ECB purchases bonds from weaker states?
a deteriorating balance sheet