Fire crews and RSPCA officers have been digging by hand in an effort to rescue a 12-week old puppy trapped underground in County Durham.
The Staffordshire bull terrier, called Sasha, became trapped on Thursday afternoon while being taken for a walk by his owners.
The pet fell down what is thought to be an old drainage channel on farmland at Cassop, near Spennymoor.
Representatives from Weardale Search and Rescue said the fissure was too narrow for a person to get in, so efforts are being made to widen the opening so that equipment can be lowered to get the animal out.
Station officer Peter Matthews, of Durham and Darlington Fire and Rescue Service, said: "The fissure stretches for at least 50 yards underground.
"A couple were out walking their two dogs and strayed off the public footpath and the dog fell into the hole.
"We tried for about five hours to try to get to the animal, but at about 1900 GMT of Thursday we had to call off the operation for the night."
Food and water has been lowered to the dog.
Attempts have been made to gauge the condition of the animal with a home camcorder which was lowered on a rope.
A local firm answered an appeal for a mechanical digger to widen the entrance to the fissure.
Mr Matthews added: "The fissure is very narrow and we need to be able to widen the entrance if the FSPCA can get equipment down there to get Sasha out.
"We know she's alive because we can hear her down there.
"We've been using our hands and spades to dig down, but we have to be careful we don't cause a collapse."