Police told people living in the street opposite the site not to be concerned but many closed their windows to avoid the smoke.

Ann Harrison watched the commotion with her grandchildren Megan, 16, Ryan, 13 and their cousin Rebecca, 11.

The 83-year-old said: “It was pretty scary. There was all this black smoke everywhere.

“They came around and told us exactly what they were doing and we heard several explosions throughout the afternoon.

“All the children were excited about everything that was going on and lots of people stopped to see what was happening.”

AW bombs could be thrown by hand or projected and contained a self-igniting phosphorus chemical which is believed to explode on impact.

The bombs may be linked to the former Royal Ordnance munitions factory at Kirkby which employed more than 10,000 people – including 8,000 women – to produce detonators and fill shells.

The busy factory, built on a site that later became Kirkby Industrial Estate, produced 10% of all the ammunition used by Britain in World War II.

Similarly, the grenades may have been linked to Kirkby Home Guard, which was staffed by both local people and workers at the factory.

The bombs were discovered around 2.30pm yesterday, and disposal experts completed their work just after 8pm.