A woman is seriously injured in hospital after she was stabbed in the chest.
Police and paramedics rushed to a property in Borehamwood at around 8am.
Multiple police cars and ambulances were pictured in Ranskill Road, while the air ambulance landed in Three Fields, off Gateshead Road.
Police and ambulances at the scene
A police spokesperson said: "Police were called at just after 8am today (Monday 23 November) to reports of an assault in Borehamwood.
"Officers, the East of England Ambulance Service and the air ambulance attended a residential property in Ranskill Road.
"A woman, found with stab wounds to her chest, was taken to hospital where she remains in a serious condition."
Police have confirmed a 17-year-old boy has been arrested on suspicion of GBH.
He is in police custody at this time.
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