To expand on Sid's answer, for those who are interested.
Unfortunately, it is likely to continue for a fair while. Estimates given by ordnance disposal experts in Belgium by the (BBC in 1998) and by The Telegraph in 2013 estimate that the last un-exploded munitions from WW1 won't be removed for another 50 to 400 years.
It is estimated that for every square metre of land on the western front one ton of explosives were fired, and that as many as one in 4 shells failed to detonate. (BBC, Legacies of the Great War). In the Ypres Salient alone it is estimated that 300 million dud shells were fired. (The Daily Mail, 2013)
To this day, Belgian and French farmers collect what is known colloquially as the Iron Harvest. Farmers will discover tonnes of un-exploded ordnance each year when ploughing or otherwise maintaining fields and will place them at the side of the road before notifying the authorities. These will then be collected by ordnance disposal experts and destroyed.
It's also believed that a small number of large un-exploded mines are lost in Belgium and France. Although, I can't find a source that gives a number I have found the following on thegreatwar.co.uk.
Some of the tunnels were built with the aim of laying an explosive charge at the far end in order to blow a mine under the enemy's position. This was treacherous work and many tunnellers from both sides of the Front Lines died in tunnel collapses, underground explosions and suffocation. In some cases it is known that the explosive charge did not go off, and these particular tunnels with their unexploded mines still pose a potential hazard today.