Traffic chaos in the Belgian capital city of Brussels, where European Union leaders are holding a summit to deal with issues including the refugee crisis and threats by Britain to quit the EU, is being blamed on hungry mice.

Reuters reports that the city has been plagued by tunnel closures due to crumbling concrete. “Now the Belgian capital’s regional parliament has been told that repairs are being held up because original construction plans have been destroyed — apparently eaten by rodents,” the story reports.

The plans for construction of the tunnels in the city, which has what is often called the most congested traffic in Europe, have apparently been stored for decades in the pillars under a bridge, where it appears that mice got ahold of the plans and ate them.