It is understood the man arrested in connection with with the death of seven-year-old Nikki Allan is 43-year-old Steven Grieveson.
Nikki was found in a derelict building near to her family home at Wear Garth in Sunderland in October 1992. She had suffered 37 stab wounds.
Mr Grieveson has been bailed pending further enquiries.
The mother of murdered schoolgirl Nikki Allan has spoken from hospital of her shock at hearing that police had arrested a man on suspicion of killing her daughter 21 years ago.
Seven-year-old Nikki was murdered in 1992.
Her body was found in a derelict building close to the family's home in a derelict warehouse in Sunderland.
Nikki's mother, Sharon Henderson, collapsed on Wednesday while working on her campaign for justice for Nikki.
Police officers visited her at Sunderland Royal Hospital to tell her that an arrest had been made.
Doctors believe Ms Henderson may have suffered a stroke triggered by stress.
Northumbria Police say that a 43-year-old man has been questioned and bailed.
A man has been arrested and released on bail in connection with the murder of a seven-year-old girl more than two decades ago.
Nikki Allan was discovered in a derelict building close to her home in Sunderland in 1992.
A 43-year-old man arrested on suspicion of murdering Nikki Allan 21 years ago has been bailed pending further enquiries.
Nikki Allan's mother Sharon Henderson has been fighting for justice since her daughter's murder.
In October a vigil was held to mark 21 years since the 7-year-old's body was found beaten and stabbed, yards from her home.
Friends and relatives gathered where she was discovered.
The investigation into Nikki Allan's death has been ongoing for 21 years.
In September officers from Northumbria Police's major crime team worked with the Crimewatch programme to film a reconstruction.
At the time detectives said they were following a number of new leads after it was broadcast.
Police are keen to speak to anyone who lived in or hung around the area where Nikki was found dead on October 8, 1992.
The 7-year-old's body was discovered in the Old Exchange Building, near to her family home at Wear Garth, Sunderland.
A 43-year-old man has been arrested on suspicion of her murder.
Police have arrested a 43-year-old man on suspicion of the murder of Nikki Allan. He is currently in police custody helping detectives with their enquiries.
Nikki Allan was seven years old when she was found dead on October 8, 1992, in the then-derelict Old Exchange Building, near to her family home at Wear Garth, Sunderland. The investigation into her death has been ongoing for the last 21 years.
A vigil was held to mark 21 years since the murder of a schoolgirl in Sunderland. Nikki Allan was seven years old, when she was found beaten and stabbed, yards from her home.
Friends and relatives gathered where her body was discovered, and brought pink roses to lay on her grave.
Sunderland reporter Julia Barthram reports.