RAIDERS who tied up a young mother before setting her house on fire must have known her baby son was in the same room, police said last night.

Four-month-old Alexander Gallon died in the blaze at the house in Cowgate, Newcastle, on Sunday night.

Last night, police revealed that a woman in her early 20s had been arrested and later bailed - but they said they were still hunting two arsonists.

Officers said the men were masked when they beat up Danielle Wails and bound her wrists after she answered the door.

They said the thugs knew there was a baby in house when they started the fire - because they would have heard it crying.

Detective Superintendent Barbara Franklin said: "It is difficult to comprehend the wickedness of anyone who would do such a thing.

"To say this was horrendous is an understatement.

"There is no way they could not have known that baby was in the house.

"It would appear their intention was to kill them both, if they have in fact locked that door."

After being knocked unconscious, the 21-year-old mother was woken by the smoke from her blazing sofa.

The raiders had bound Ms Wails's hands with a length of telephone cable. Using her tongue, she dialled 999 and screamed for help.

Firefighters kicked down the locked front door, at her home in Link Road, and rushed Ms Wails to hospital. But they were unable to save Alexander.

Det Supt Franklin said: "At 10.30pm on Sunday, Danielle was at her home in Newcastle with her only son, Alexander.

"The front door was open, as is normal for that part of town, when two men wearing black clothes and masks entered the house.

"They punched her and kicked her and she fell to the ground and passed out.

"She lay unconscious on the floor of the living room, where her baby was sleeping on a sofa.

"Her hands were tied in front of her with what is believed to have been a telephone cable.

"The seat of the fire was between her and the baby."

The officer added: "We need people to come forward and help us catch these two people. If ever there was a crime that the public are going to help in, it should be this one.

"We want to know who saw two men on the estate wearing dark clothes at 10.30pm that night. We believe we may be able to find CCTV camera footage of the pair."

A post-mortem examination was carried out on Alexander yesterday afternoon.

Last night, after being released from hospital, Ms Wails went to stay with relatives.

The baby's father, 21-year-old Robert Gallon, was believed to be comforting her.

Mr Gallon did not live with Ms Wails, but remained in contact with her and had regular access to his son.