At least eight police cars have descended on a residential road in Worthing after an officer was bitten by a dog.
A spokesman for Sussex Police said an officer had been bitten on the leg by a dog while assisting a social worker in Selden Road, shortly before 9.30am.
The social worker had been visiting the address over concerns to the welfare of the female resident, police said, whose dog then bit the officer.
The dog was safely restrained and the officer was taken to Worthing Hospital for treatment, police added.
A 46-year-old woman has been arrested on suspicion of assault on police and of causing grievous bodily harm and is in custody for interview and further enquiries, said police.
Pictures from Selden Road show officers on the scene, blocking the road with cars and a riot van.
Eyewitnesses had earlier reported the large number of police vehicles driving through Broadwater towards the town centre.