Police had “previous contact” with a mother and her estranged husband before she allegedly murdered her two young children.
Officers refused to divulge the nature of, or when they had, dealings with Fiona and Paul Donnison, but said it would be reviewed in inquiries.
Neighbours said the couple were living together in Heathfield, East Sussex, until they separated and their house put up for sale before Christmas.
A Sussex Police spokesman said: “We are aware of previous contact with police in relation to this family.
“This will be reviewed, in liaison with appropriate agencies, as a matter of standard procedure and also in order to help inform the current police inquiry. We cannot release further information at this time as it could prejudice the investigation.”
An Independent Police Complaints Commission (IPCC) spokesman said the force had not referred any matter to it relating to the case.
Detectives were still waiting last night to question former City worker Mrs Donnison (43) over the murders of her young son and daughter.
She was arrested after she went to Heathfield police station yesterday morning in a distressed state to ask officers to search her car.
When police forced entry to her silver Nissan in Mill Close, they found the bodies of Harry (3) and Elise (2) in two large holdalls in the boot.
Post-mortem examinations are to take place at King's College Hospital, London, to determine cause of death.
Their mother was stable in Eastbourne District General Hospital with “apparent self-harm injuries”.
The Nissan was towed away for analysis and a cordon was in place around the family's detached house in Sheepsetting Lane, close to where the car was parked. Police said officers were not looking for anyone else in connection with the deaths.