Swiss bank Credit Suisse said Monday that it may face a highly significant loss resulting from a default by a US-based hedge fund on margin calls that it and other banks made last week. In a brief statement, Credit Suisse didn’t identify the significant hedge fund or the other banks affected, or give other details of what happened.

Following the failure of the fund to meet these margin commitments, Credit Suisse and a number of other banks are in the process of exiting these positions, the company said.

While at this time it is premature to quantify the exact size of the loss resulting from this exit, it could be highly significant and material to our first-quarter results, notwithstanding the positive trends announced in our trading statement earlier this month, it added. Credit Suisse said that it plans to issue an update in due course.

A margin call is triggered when investors borrow using their stock portfolio as collateral and have to make up the balance required by banks when the share prices fall and the collateral is worthless.