Ten days after two 10-year-old girls in Britain disappeared, police had no clues to where the girls might be or whether they were alive or dead.

Holly Wells and Jessica Chapman vanished Aug. 4 while walking near their homes in the village of Soham, 12 miles northeast of the university town of Cambridge in southeastern England.

Detectives spent Tuesday night digging up a site about 10 miles from where Holly and Jessica were last seen, but found nothing.

"This has been a particularly long and distressing night for the two girls' parents," said Detective Chief Inspector Andy Hebb, "and my heart goes out to them."

A man told police he had found two mounds of freshly disturbed ground at the site, where he had earlier reported hearing screams the night the girls disappeared.

Other people have said they saw two children struggling with the driver of a green car in the area at the time.

Detectives have contacted hundreds of potential witnesses in a bid to find the girls, and have also used the sex offenders register to trace known pedophiles in the area.

The girls used the Internet shortly before their disappearance, but police said the pair had not communicated with anyone during their 20 minutes online.

The case has generated immense news media interest in Britain and prompted rival tabloid newspapers to offer a $1.72 million reward for vital information about the missing girls.

The tabloids have put the faces of the missing 10-year-olds on front pages all around the country.

Ten thousand telephone calls offering clues have been logged by police, and soccer superstar David Beckham has come forward appealing for information.

At the time they disappeared, both girls were wearing the red jerseys of Manchester United, the team Beckham plays for.

In Britain, abductions of children by strangers are considered rare, but several recent cases have increased concern among parents about the safety of their sons and daughters.

The girls' case follows by months the disappearance of 13-year-old Amanda Dowler. In May, after a six-week search, the tabloid Sun offered a $145,000 reward for information that would help police trace Amanda. She remains missing.

Public concern has been heightened since the kidnap and murder of 8-year-old Sara Payne in July 2000 by a convicted child molester. The man's neighbors did not know of his record, and the case caused a national outcry.

The Associated Press contributed to this report.