Detectives were last night questioning an 18-year-old youth in connection with the murder of a 12-year-old girl found stabbed to death at her North-East home.

Natalie Ruddick was discovered by her 15-year-old sister, Emma, lying in a pool of blood in her bedroom when she returned home from school.

Police said Natalie was stabbed several times at the family's home on the New Mills estate in the Arthur's Hill area of Newcastle on Wednesday afternoon.

An 18-year-old local man was arrested and was last night helping with inquiries.

Speaking at a Press conference yesterday, Detective Superintendent Tony Thornton, who is heading the police inquiry, said the girl had died as a result of the "numerous stab wounds". So far, they have not established a motive.

"I cannot begin to describe how distressing this is for her family," he said.

"She just happened to be off school because she was feeling unwell - and then for them to come home and find her like this.

"Everyone involved in the inquiry is in shock."

Natalie, a promising cross-country runner, described as a "lovely, bubbly" girl, had been staying at home because she was unwell on the day of the attack, which is believed to have taken place between 10am and 2.30pm.

Police believe her assailant's clothes may have been covered in blood as he left the scene, and have appealed for witnesses who may have seen anything unusual at the time, or even seen the attacker dispose of clothes or a weapon.

Det Supt Thornton said there had been no sign of a break-in at the house.

He declined to comment on whether the local man helping with inquiries knew the family. Det Supt Thornton added: "We don't have a clear motive but we are not ruling anything out."

Natalie's friends yesterday laid flowers outside the family's three-storey maisonette.

One 14-year-old girl described the horrific scene as she went to call on Natalie after school.

She said: "I went round to the house at about 4.30pm to see how Natalie was and Emma was crying her eyes out on the doorstep.

"She just kept saying 'Natalie's dead, Natalie's dead'.

"When she found Natalie, she gave her mouth-to-mouth but couldn't do anything. It was too late to save her."

Natalie, one of six children, lived with her mother, Dawn, and father, Michael, a carpet cleaner.

Four of her brothers and sisters were twins - Emma and Steven, 15, and Chris and Zoe, ten. She also had a 16-year-old sister, Claire.

Natalie was a year eight pupil at All Saints School in Newcastle's West End.

Family friend Dawn Pattinson, 38, said: "Her parents were out all day and her brothers and sisters were at school.

"I spoke to her mum and dad last night and they were distraught.

"She was a cheeky, lovable little girl and full of life. I can't believe she has gone."

Natalie's friends were offered counselling following an assembly yesterday, where the news was broken to the school.

All Saints College principal James Colquhoun said: "It is with great shock and sadness that we have heard about the sudden death of Natalie.

"Natalie was a well-liked student and represented the college in both city and county cross-country championships.

"Our thoughts and prayers go out to her sisters, brothers, parents and friends.

"Natalie will be greatly missed in our college community."