The question being asked: Have errors been made by police?

As forensic science teams search heathland site near Newmarket, the quality of the investigation comes under scrutiny

Almost from the moment the tearful parents of Holly Wells and Jessica Chapman appeared on television the plight of the missing 10-year-olds gripped the country.

Photographed smiling in their Manchester United shirts just an hour before they wandered off from a family barbecue, the girls became the subject of one of Britain's biggest police hunts.

But yesterday as police searched heathland near Newmarket nine days after they disappeared questions were being asked about the quality of the police inquiry as well as the safety of our children.

Firstly, the police took four days to interview a taxi driver, who seemed to have witnessed the girls being driven from Soham. Secondly, the dog walker who heard screaming on the heathland reported the incident to police on Tuesday last week but his account was filed with the many other thousands of reports. It appears to have been given a low priority until the same man while out jogging reported finding two patches of recently dug earth.

The massive police hunt for Holly and Jessica, that involved 17 police forces and more than 320 officers, began on the evening of Sunday 4 August.

The girls' parents did not realise they were missing until about 8.30pm when they went to Holly's bedroom and found they had gone. The children were later discovered to have gone for a wander around their home town of Soham, a quiet market town on the Cambridgeshire fens.

Hundreds of volunteers and police officers spent a fruitless night searching for the girls in the town and surrounding countryside.

The following day the children's distressed parents Sharon Chapman, 43, her husband Leslie, 51, Nicola Wells, 35, and her husband Kevin, 38, appeared at a press conference to appeal for help in finding their daughters.

Mr Wells said: "They were in and out playing. We were having a family barbecue. And when we went to check on them they weren't there." He said the girls might have left the house to buy some sweets.

As the hours and days went by without any sign of the children concerns that they may have been abducted grew. Again and again the girls' families made appeals through the media, hoping to jog someone's memory or conscience. The case played on every parents' fear – that their child could be snatched by a stranger. The added terror was that Soham was such a seemingly safe, close-knit community; surely if something like a double abduction could happen there, what chance the rest of the country?

A ray of hope came when a woman living in the village of Little Thetford, about eight miles away, reported seeing two happy looking girls wearing Manchester United tops walk past her house on the main A10 road at 6.45am on Monday, the day after they disappearance.

But this sighting was typical of the inquiry, a false lead that merely distracted from the task of finding Jessica and Holly. Other false leads included inquiries into the girls' home computers and the possibility that they had been lured to their deaths by a paedophile who had contacted them through an internet chat room. A white van was also seized and searched. Two men were arrested and released. CCTV film of the girls walking around the town and a reconstruction using child actresses attracted huge media attention.

But as thousands of reports flowed into the police inquiry, one seemingly crucial clue remained untouched.

Two days after the girls had disappeared Ian Webster, a 56-year-old taxi driver, had contacted Cambridgeshire police with what appeared to be a vital sighting.

He would later tell them that he had seen a man "thrashing" his arms about as he drove erratically away from Soham at about 7pm on Sunday with two children in the car.

Mr Webster, who had just picked up a fare from nearby Ely, first noticed the car, thought to a Vauxhall Vectra, or possibly a Peugeot 405, near a roundabout on the A142, south of Soham.

Yesterday he recalled: "It was driving in a very, very erratic manner. It was wavering all across the road on both sides of the road hitting the banks both sides of the road.

"There were two small children obscured from vision, one in the front seat, one in the back seat behind the passenger seat."

After following the car for about seven minutes it turned off on the outskirts of Newmarket.

Mr Webster said: "At first I thought the driver was drunk or a father driving with children, but he was demented."

But despite this apparently clear sighting the police did not interview him for four days, even though he contacted them twice more.

Once he realised the significance of what he had seen Mr Webster, who was on a working break in Wales, first considered speaking to police in Brecon on Tuesday – two days after the 10-year-olds were last seen.

He said he was told by a member of the public to contact them the next day as he would need to speak to a CID officer, and there were none available at the time.

He first contacted the local police on the Wednesday, leaving his mobile phone number. He was told about an hour later that Cambridgeshire police had been informed.

Mr Webster returned home to Newmarket on Friday, where he again contacted police. He spoke to another officer on Saturday and was finally telephoned on Sunday morning.

He said: "I was cross I didn't get a response after the second prompting and even more cross after the third.

"My views are that in something of this nature time would be of an essence and time was a priority."

Mr Webster added: "I don't want an explanation for it. I think that the parents of the children concerned might have to seek an explanation for it."

Detective Chief Inspector Hebb told reporters at a news conference yesterday afternoon that his officers were having to cope with a flood of information and thousands of reports when the taxi driver's report came through.

"All I can do is reiterate that every piece of the vast amount of information we have received is extremely important and treated seriously. Each and every piece of information is assessed and prioritised according to the current direction of the inquiry."

He went on: "That may mean information may subsequently become more significant and vice versa when assessed against other new information." Det Chief Insp Hebb added: "It is an incredibly time-consuming process but you can be assured that we have tapped into every available resource."

More than 7,500 calls have been made to the police hotline, which are graded by officers according to their assessment of their urgency and then follow-up interviews take place.

On Monday, after receiving the report of their interview with Mr Webster, the police put out an appeal for more information describing the sighting as a potential breakthrough.

But yesterday afternoon the police gave the news that the girls' parents were dreading – two mounds of earth had been found.

Police had been alerted to the site by a man out jogging at about 11.30am. The same man had reported to police hearing teenagers screaming on the night of the abduction. The site is only two miles south of where Mr Webster last saw the green car turn into a housing estate.