Context : The Fermi bubbles are part of a complex region of the Milky Way .
This region presents broadband extended non-thermal radiation , apparently coming from a physical structure rooted in the Galactic Centre and with a partly-ordered magnetic field threading it .

Aims : We explore the possibility of an explosive origin for the Fermi bubble region to explain its morphology , in particular that of the large-scale magnetic fields , and provide context for the broadband non-thermal radiation .

Methods : We perform 3D magnetohydrodynamical simulations of an explosion from a few million years ago that pushed and sheared a surrounding magnetic loop , anchored in the molecular torus around the Galactic Centre .

Results : Our results can explain the formation of the large-scale magnetic structure in the Fermi bubble region .
Consecutive explosive events may match better the morphology of the region .
Faster velocities at the top of the shocks than at their sides may explain the hardening with distance from the Galactic Plane found in the GeV emission .

Conclusions : In the framework of our scenario , we estimate the lifetime of the Fermi bubbles as \approx 2 \times 10 ^ { 6 } yr , with a total energy injected in the explosion ( s ) \gtrsim 10 ^ { 55 } ergs .
The broadband non-thermal radiation from the region may be explained by leptonic emission , more extended in radio and X-rays , and confined to the Fermi bubbles in gamma rays .