More than £100,000 is now being offered to nail the killer of schoolgirl Sarah Payne, police will reveal today.

Detectives say this is the largest reward ever put up in Sussex to catch a criminal.

A Press conference is due to be held this afternoon at which police will reveal the exact amount being offered.

The reward, for information leading to the arrest and conviction of Sarah's killer, includes £10,000 from the Argus, plus money from other newspapers, private companies and individuals.

Sarah's grandfather, Terry Payne, said: "The rewards show how much Sarah's murder has touched people throughout the country. Speaking on behalf of all the family, I want to say thank you to all those concerned. We can only hope and pray it brings information forward. Someone out there knows something and I would plead with them to do the right thing." Detective Superintendent Alan Ladley, who is heading the inquiry, said: "This is the largest reward ever offered in Sussex. We are extremely impressed by the public response to Sarah's murder and we fully support anything that helps bring her killer to justice."

Eight-year-old Sarah was kidnapped near her grandparents' home in Kingston Gorse, East Preston, on July 1. Her body was found on July 17 off the A29 near Pulborough. She had almost certainly been sexually assaulted, then strangled or suffocated.

Police at today's Press conference in Littlehampton will produce a blue dress identical to that worn by Sarah on the day she was murdered.

Officers contacted the manufacturers in Taiwan and asked them to reproduce the dress, which the Paynes bought from Quality Seconds. Police are still looking for Sarah's clothes in the hope they will produce a forensic connection with her killer.

Detectives admit there are no major breakthroughs in the inquiry, but they remain optimistic.

They are still appealing for information about a white van seen near the spot where Sarah was kidnapped and want to hear from all drivers of white vans or motorists who saw white vans in the area on the evening of July 1.

A spokesman said: "Our inquiries are very much continuing and active."