NHS staff and patients in York may have come face to face with murder suspect Mark Hobson after the brutal killing of twin sisters Claire and Diane Sanderson, it emerged today.

Detectives were today studying CCTV footage which caught Mark Hobson walking through the grounds of York Hospital at 2am on Sunday, near the entrance of the accident and emergency department.

His mother, Sandra, was duped into driving him there from her home at Camblesforth, near Selby. Police said he was not believed to be injured and it is not known whether he went inside the hospital.

Six hours later, the decomposed body of Hobson's girlfriend, Claire Sanderson, 27, was discovered wrapped in plastic bin liners on the floor in the flat in Camblesforth, near Selby.

Forensic evidence showed that her twin sister Diane, who was found dead in the same room, had been sexually interfered with. Both sisters were naked. A hammer was recovered from the flat.

At about 11.30am on Sunday, James Britton, 80, and his wife Joan, 82, were found murdered at their detached house in Strensall, just three miles away from the hospital. They had both been stabbed in the back.

Mr Britton was found dead in the sitting room, his wife in the hallway.

Detective Superintendent Javad Ali, who is leading the inquiry, said there were no signs that the Brittons had put up any defence, which made the attack "even more horrible".

The nationwide hunt for shaven-headed, scar-faced Hobson continued today, but officers admitted they were still no closer to finding him.

More than 22 houses have been physically searched by police, including a house in Hempbridge Road, in Selby, which was raided last night.

Terrified mum Lynn Skilbeck spoke out after officers in full body armour, some with dogs and others carrying powerful rifles, sealed off both ends of the street and surrounded her semi-detached home.

She said she had heard noises coming from the attic of the empty house next door, which she put down to an animal - until yesterday evening.

"I went into the kitchen for something, looked up and there were armed police everywhere," she said.

"One of them said: 'Move back', then there was a knock on my door and they said: 'We have to evacuate you'.

The council house which police swooped on had just been vacated by tenant Gwen McIntyre.

Miss McIntyre now lives at the Royal Oak pub, in Ousegate, Selby, where she works as manager and bouncer.

She said: "I handed the keys in to the council on Monday. I also gave keys to my house to two of my friends, one of whom was helping me to move my furniture and another who was storing furniture at my house for a time."

She said the friends lived in Abbots Road, Selby, where two women were arrested and bailed after houses were raided there on Wednesday.

Mother-of-two Miss McIntyre said: "I can only assume they found the keys to my house during the Abbots Road raid. But I don't really know because the police haven't spoken to me and nobody has let me know anything. All I know is that a few friends rang me last night to say police were swarming all over my house and that Mark Hobson might be in my attic."

Meanwhile, in a private meeting at York Police Station, villagers from Camblesforth and Strensall asked police officers what steps they were taking to bring whoever killed the four victims to justice.

John Scott, a member of Strensall Parish Council, said the meeting had brought the villagers up to date with the murder inquiries. He said: "People said they were frightened that he (Hobson) was still in the area and we were reassured that the police were doing everything they could to find the chap and arrest him."

A mobile "cop shop" has been moved into Camblesforth to reassure residents and glean more information from the public. The portable police station is now sited in the grounds of Camblesforth Primary School.

The station will be manned 14 hours a day, from 8am to 10pm.

Meanwhile, Kelly Williams, described as the best friend of Claire, said she did not think Hobson would have gone far. "I do believe he's still in the Selby area, it's where he knows," she said. "But he has got a very charming side, and I just want to warn people, don't be taken in by him - please, for God's sake, don't be taken in by him."

Meanwhile, it was also reported today that Hobson may have "lost his grip on reality" after his ex-wife, Kay, stopped him seeing his children, when his drinking became excessive.

Updated: 10:17 Friday, July 23, 2004