Officers in Dundee attended a property on Troon Avenue on Friday afternoon as part of an inquiry into the disappearance of Bennylyn Burke and two children.
They had been reported missing from South Gloucestershire on Monday, March 1.
A 50-year-old man has been arrested and charged in connection with the deaths of Bennylyn and her daughter, Jellica.Enquiries are continuing to establish their whereabouts.
The man is expected to appear at Dundee Sheriff Court on Monday.
A second child reported missing has been traced and is being supported.
Detective Superintendent Graeme Mackie, of Police Scotland’s Major Investigation Team said it was a “complex inquiry” which involved officers in Dundee as well as specialist resources across Scotland.
He said: “We are now treating the disappearances as a murder investigation.
“I would urge anyone with any information to please come forward and speak to us.“This is a complex enquiry involving both local officers in Dundee and specialist resources from across Police Scotland.
DS Mackie added: “Bennylyn’s next of kin have been updated on the arrest and are being supported by colleagues from Avon and Somerset Police.
“Our thoughts are with her family and friends at this very difficult time.”He confirmed there would be an increased police presence in the area for a considerable period of time.
Contact Police Scotland via 101, quoting incident 1434 of 5 March, 2021.”