Germany could use emergency measures to respond to the possible panic of the market in the event of a Brexit without an agreement, said an official with direct knowledge of the issue, such as banning bets on stock collapse, a measure used for the last time during the financial crisis.

Germany is the most important of a group of countries, including Italy and the Netherlands, which assesses a temporary ban on short-term sales of shares. The Frankfurt stock market is one of the largest in Europe.

Although emergency measures have not yet been implemented, preparations underline the alertness of the continent in the face of uncertainty about the outcome of the negotiations to ensure an orderly exit from the European Union from the European Union.

In the event of a stock run, authorities in Frankfurt, Amsterdam and Rome could limit the form of operations known as short sales, authorities in those countries told Reuters, to contain any exaggerated price variations.

British Prime Minister Boris Johnson has promised to remove the United Kingdom from the block on October 31, regardless of whether or not a divorce agreement has been reached. He has not explained how he will deal with a law passed by Parliament that stipulates that the United Kingdom cannot leave the EU without an agreement.

Many bankers, however, fear that failure in negotiations this week could hit markets much earlier.

The market regulator in Germany, BaFin, would probably identify a group of companies especially vulnerable to the economic repercussions of Brexit to temporarily ban short-term sales of their securities, said a second source with knowledge of the issue.

Germany has done it before. During the financial crisis of the past decade, BaFin identified several banks and other companies to stop short sales of its shares.

Earlier this year, the regulator applied its first ban on short sales of Wirecard shares (DE: WDIG). The measure lasted two months and sought to limit volatility.

While investors can also make short sales of corporate debt, BaFin has focused primarily on the shares, the second source said.