By Warsaw correspondent James Coomarasamy

Two Polish army helicopters have bombed the frozen Vistula River in an attempt to break the ice around Europe's longest wooden bridge.

Temperatures are set to plunge again

According to the local authorities, the bridge, which is located some 60km to the west of Warsaw, is in danger of collapsing unless urgent action is taken.

The helicopters lowered more than a ton of explosives onto the frozen Vistula River early in the morning. Moments later they were detonated marking the beginning of what will probably be a lengthy operation to save the 1,200 metre long structure.

Cold snap

According to the local mayor around six kilometres of ice became wedged beneath it during the recent unseasonably cold snap.

Now the ice is pressing against the bridge's low supports giving the authorities cause for concern.

Officials say the ice offers a double threat. Not only is it putting the bridge in danger of collapsing, but by acting as an effective dam it could cause flooding in the surrounding areas.

With temperatures in Poland looking set to plunge again after a brief thaw, the efforts to save the bridge haven't started a moment too soon.