Builders got a nasty shock when their machines dug up a highly-explosive First World War live grenade.

Construction workers building houses on the site near Bingley uncovered the hand grenade in a storm drain.

Police and the Army's bomb disposal unit, from Catterick, North Yorkshire, were alerted and went to the site at Dobb Kiln Lane, Dowley Gap.

A spokesman from the Army bomb disposal unit said: "The grenade was very corroded so it is difficult to be precise about the details. We think it was a British number five hand grenade which dates from around 1916. It is highly explosive and anti-personnel."

A construction worker who was on site when the grenade was discovered said: "We were digging the ground with a 360 digger when someone spotted an unusual-looking object.

"We turned the machine off immediately and saw that it was some kind of grenade. I was really scared because I did not know whether or not it was safe. It could have exploded.

"The soil is brought in from all over the country so the grenade could have come from anywhere."

Inspector Tom Horner, of Keighley Police, said: "Police were called to the site just after 9am.

"We contacted the Army's bomb disposal unit at Catterick immediately. When the unit arrived the site was cleared and the grenade was detonated in a safe area."

Les Irwin, 36, bar manager at the nearby Fisherman's Pub in Dowley Gap, said: "We heard a lot of commotion and saw the Army's bomb unit arrive with a police escort.

"We weren't forced to evacuate so it was business as usual."

Five houses are being developed on the land by Bradford firm MD Construction.

They are scheduled to be completed and up for sale in eight weeks' time at a market price of around £500,000 each.

The company declined to comment. It has been told by the bomb disposal unit to contact them immediately if workers find any more grenades.

Inspector Horner said: "The construction workers acted in exactly the right way by calling us immediately and should be congratulated on the way they dealt with the situation."

Another builder on the site said: "We found a helmet before Christmas but we didn't keep it because it was badly damaged."