Police hunting missing schoolgirl Sarah Payne said today they had released one of the men arrested in connection with her disappearance.

The man, in his thirties, was given police bail but detectives were still questioning another man about the missing eight-year-old.

As the search continued for Sarah, who vanished from near her grandparents' home, police said they were intensifying efforts to find her.

Sussex Assistant Chief Constable Nigel Yeo said: "It's obvious that the situation gives increasing cause for concern as the time goes on."

He said police have received 800 calls offering assistance in the case and that more than 300 members of the public were currently helping specialist teams of officers comb the countryside west of Worthing, near where Sarah disappeared on Saturday evening.

He said police were working through information from members of the public and their own records - including the register of known sex offenders - in an effort to track down the youngster.

Police may also stage a reconstruction of Sarah's last known movements.

The news came as Sarah's parents said the schoolgirl's brothers and sister had been left distraught by the disappearance.

Her father Michael said the agonising wait was beginning to "hit home" to Sarah's brothers Lee, 13, Luke, 11 and six-year-old sister Charlotte.

Mother Sara added: "The little one, Charlotte, keeps asking after Sarah now, saying: 'Find Sarah', things like that.

"It is starting to hit home and affect them."

Mrs Payne told how she and her husband, both 31, had hardly slept or eaten since their daughter went missing on a family day out on Saturday.

She sobbed in front of television cameras today as she made a fresh appeal for her daughter's return, saying: "If she can see or hear us, we are coming to get you darling.

"We just want our baby back."

Volunteers were today helping police search Highdown Hill, on the outskirts of Worthing close to the A259.

Detective Superintendent Alan Ladley, who is leading the inquiry, renewed his appeal for information but said bad weather had been hampering the search.

"We still need the public's help. We need people to come forward if they were in the area.

"If anyone knows anything or has suspicions about anyone who may be holding Sarah, please come forward."

Sarah vanished from fields at Peak Lane, in West Kingston, near Ferring, while visiting her grandparents with her family, who live in Surrey.

Det Supt Ladley said the mood of his officers was turning to frustration.

"There's a hope that Sarah is still alive but extreme frustration."

The man released on bail today is not thought to come from the area.

The second man, who is in his forties, is still in custody. Police have until midnight tonight to either charge or release him, or apply to a magistrate for more time to hold him.

He was arrested at his home in St Augustine Road, Littlehampton, on Sunday night.

His flat has been searched and a white van removed from outside.

Sarah was last seen wearing shiny black shoes with velcro fastenings and a dark blue Fred Perry-style tennis dress. Her hair is cut in a bob.

The father of a ten-year-old girl snatched by a paedophile last year sent his support to the Sarah's parents today, telling them: "Never give up hope".

More than 100 soldiers and dozens of police officers searched an area of East Sussex for the girl and her best friend when they went missing on January 19 last year.

After four agonising days of waiting, the girls were found in the Eastbourne flat of known paedophile Alan Hopkinson, 45, jailed for life in December last year for abusing them.

Today the 32-year-old father of one of the girls said Sara and Michael Payne should "never give up hope".

He said: "The four days our daughter was missing were the worst of my life."