A divorced British man is being questioned by police in France on suspicion of slitting the throats of his two children, reports Sky News.
The bodies of the youngsters aged five and 10 were discovered in his flat in Saint-Priest, a suburb south-east of Lyon, on Saturday.
A judicial source told the AFP news agency that a knife, which is thought to have been the murder weapon, had been found.
The unemployed man and his ex-wife, an assistant accountant, were said to have recently gone through a difficult divorce.
She had moved out of the property and the children were said to have been living with her in the Isère region after she won custody. The source said the father, 48, had visitation rights but only in the presence of another person.
This weekend was the first time he had brought the children home to his apartment, the source added.
The youngsters were said to have arrived at the property the small, four-storey building on Friday. Their mother had reportedly been worried about the visit and returned to the flat on Saturday afternoon.
She is said to have seen her ex-husband, his clothes stained with blood, in the stairwell and raised the alarm.
French newspapers reported that several witnesses said the man had fled the scene on roller skates. He was later taken into custody in Montplaisir, in the eighth arondissement of Lyon, a couple of miles away.
Neighbours said the couple had separated several years ago.
Read more of this report from Sky News.