Human bones which were unearthed by landscape gardeners at a house in Purley could have belonged to a child, according to the man who found them.
Officers were called to the address in Riddlesdown Road after the workers found the remains buried underneath the driveway yesterday.
Several bone parts - including what appeared to be a human skull and a femur - were seized and taken for analysis.
Experts have since confirmed, by looking at photos, that the bones are human, and they have now been taken for examination by anthropologists to establish their age.
Police are investigating the circumstances of how the bones ended up in the driveway.
The cause of death is unexplained.
No arrests have been made.
Detective Sergeant Kenny Windsor, from Croydon CID, who is leading the investigation said: "At this early stage in the investigation it would appear that the bones have been there for many years.
"Any requirement for an investigation will be determined by the age of the bones and we're seeking the assistance of anthropologists to try and establish this, but we may also have to use carbon dating techniques to confirm their age. We are carrying out other enquiries in the meantime.
"It is an unusual discovery, but we're keeping an open mind about whether the bones were originally buried there or indeed moved there for some reason.
"We're also aware that there is an ancient Saxon burial site in the vicinity but at this stage, the direction of our investigation hinges on establishing age of the bones."
Man who discovered bones said he thinks they look really old
Landscape gardener Terry Jobson said his workers were using their digger at the property yesterday morning and had just dug into the soil when they saw the skull.
He said the teeth were no longer in the jaw but were quite close to it and then they found a leg bone and called the police.
Mr Jobson, 41, said: “We were doing a driveway and had taken a bit of soil off and as we took the soil off it was there.
“At first I think we thought it was a coconut.
“It was more of a child size but it had teeth so it wasn’t a baby’s skull and the leg bone was not too big.”
Mr Jobson and the rest of his team from Wallington based firm B&T Jobson Landscape Gardeners has not been able to work at the site since they made the discovery as police are investigating.
He said: “In my eyes it looked like it was really old and I don’t think it was new but how do I know?
“If it is 70 years old or older then it is not a murder enquiry and all they are going to be able to tell us is whether they are less than 70 years old or ancient.
“They have a police officer there day and night so no-one else can go there.”
Bone discovery has ‘livened up the Easter holidays’
The Carpenter family have lived in the house for two years and were out having breakfast yesterday morning when the discovery was made.
They got a call from one of the workmen telling them what had happened.
Mother-of-four Alison Carpenter, 41, said: "He said, 'We think we've found a skull so we better stop doing.
"We were shocked. We didn't know what to think. The builders got extremely freaked out by it.
"I thought, is a good job we have not been living here long otherwise we might have been arrested.
"It would be nice to know who it is and what happened to them.
"We have had a police officer here the whole time since it was found because it is being treated as a crime scene until they have dated it."
Her husband Michael, 46, said: "It was half a skull. It is clearly very old. It was yellow and crumbling and had dirty chalk all over it.
“It had no teeth but the teeth were lying nearby it.
"The leg bone looked a bit like something you would give to a dog.
"The kids thought it was brilliant.
"It has certainly livened up the Easter holidays.
"They are looking forward to telling everyone when they get back to school."
Their eldest child, Zac, 13, said: "It is really interesting. Not many people find a skull in their garden."