POLICE began digging up a garden in Elland today in the hunt for vital evidence.
It is believed they are involved in a top-level investigation into a murder.
Detectives at the scene off Huddersfield Road would not reveal details of the case.
But they confirmed that the team of officers working in the back garden were investigating a serious crime that took place some time ago.
The officers - all wearing navy blue police overalls - arrived at the terraced house shortly before 10am and sealed off an area of the small back garden.
Curious neighbours watched from their homes as the officers brought in a mechanical digger and a number of tools including spades.
Officers took many photographs of the scene as the digging got under way.
Police stressed that the people who live in the house were not under any suspicion.
Det Supt Phil Sedgwick, of West Yorkshire Police, is the senior investigating officer appointed to head today's inquiries.
He said: "We are conducting an investigation into a serious incident that happened some time ago, before the present occupants of the house moved in.
"The search is being conducted with their consent and they are not suspected of anything.
"We have a number of police officers digging up the garden and we are looking for evidence."
The big police operation was initially concentrated on the bottom left-hand corner of the garden.
A small flagged patio is adjoining the house and the rest of the garden is given over to grassed areas and a path.
Another garden and a grassed area run across the bottom of the garden.
The house is in the centre of a block of properties thought to be about 30 years old and is set back off Huddersfield Road, leading out of the centre of Elland.
Both back and front doors of the house were open as officers worked and the curtains were open. A woman was believed to be in the house.
One marked police van was parked outside this morning, with other unmarked vehicles.
Police said they expected the search to continue for some time.