A man is being questioned on suspicion of attempted murder and a woman held over an assault allegation after a man suffered serious head injuries.
The 56-year-old man was discovered injured at a house in Rydal Street, Hartlepool, at 10.43pm yesterday.
Cleveland Police say he was taken to James Cook University Hospital, where he is said to be in a critical condition.
A 32-year-old female was arrested on suspicion of assault and a 42-year-old man was arrested this morning on suspicion of attempted murder.
Police believe the attack may be linked to an earlier incident at an address in St Oswald's Street, Hartlepool, at 8.33pm yesterday.
Scene of crime officers were still working at the house in Rydal Street this evening, and a police car was stationed in St Oswald's Street.
Laura Smith, 21, who lives opposite the house in Rydal Street, said: "There were three police cars, a police van, two ambulances and an ambulance response car. Their blue lights were all going."
Residents were in the dark about what had happened, she added: "The police have been there all day but nobody has come to the door except to ask if we have have heard anything."
Another neighbour, who did not wish to be named, said he believed a man and woman lived at the address.
In St Oswald's Street, a neighbour said there had been 'a commotion' in the road last night.
"It was so noisy, I had to go upstairs," he said
Inquiries are continuing, and anyone with any information about either incident are asked to contact Cleveland Police on 101 or contact Crimestoppers anonymously on 0800 555 111.