A 33-year-old woman has been arrested and charged in connection with the death of three-year-old Mikaeel Kular, police said tonight.
Police did not name the woman, although it has been widely reported that the mother of the missing Edinburgh boy was being questioned by officers after a child's body was discovered in Fife, miles from his home.
The development was announced late on Saturday by Police Scotland Assistant Chief Constable Malcolm Graham, who said: "During the course of today, the investigation into the disappearance of Mikaeel Kular has continued at pace.
"Following formal identification, I can now confirm that a 33-year-old woman has been arrested and charged in connection with Mikaeel's death.
"The woman is expected to appear at Edinburgh Sheriff Court on Monday."
A major police investigation was launched to trace Mikaeel after he was reported missing from his home in Edinburgh's Ferry Gait Crescent on Thursday.
More than 200 members of the public joined police and other agencies in their searches for the youngster in the Drylaw area of the capital yesterday.
Officers searching for the three-year-old found remains - now identified as Mikaeel's - in Kirkcaldy, Fife, later that night.
Mr Graham expressed his thanks to all those who aided police in recent days.
More than 500 calls were made by the public to a dedicated phone line set up in the wake of Mikaeel's disappearance, he revealed.
He said: "I would like to again recognise the overwhelming public assistance that Police Scotland have received during the course of this very complex investigation. This includes his family and friends, with whom our thoughts remain.
"Over 200 civilian volunteers joined the search for Mikaeel within the Pennywell, Muirhouse and Silverknowes areas of Edinburgh during adverse weather conditions and cold temperatures.
"In addition, our dedicated number received in excess of 500 calls, with people wishing to provide information to help establish Mikaeel's whereabouts.
"I would like to extend my sincerest thanks to you all for your vital support.
"My thanks also go to the various external search agencies who provided essential resources, equipment and personnel during this enquiry. Police Scotland is immensely grateful for your contribution.
"Inquiries continue, led by the Major Investigation Team of Police Scotland, supported by a range of local and national specialist assets from across the country. I ask that anybody who has any information that they feel would assist the investigation contacts the police."
Mr Graham said he would be unable to answer further questions about the investigation.