The man holding a two-year-old girl in an armed siege is believed to be her father, Thames Valley Police said.
Officers were called to a house in Kidlington, Oxfordshire, at 3:40am this morning following reports a 38-year-old man was holding twin girls in a "domestic-related incident", the force said.
The unnamed man is estranged from the children's mother and does not live at the property in Morton Avenue.
Thames Valley Police said: "The man has been in regular communication with the police and one girl was released at around 9:45am.
"Officers are continuing to speak to the man who is still inside the property with the other child".
Armed officers were deployed to the address and a cordon has been placed around the property.
More top news
A similar split set up to today
The Eagles of Death Metal want to be the first to play the Bataclan when it reopens, the lead singer has said in an emotional interview.
Cheap commercial spaceflight took one giant leap closer to reality after Blue Origin successfully landed a rocket - upright - in Texas.