Four men are being held on suspicion of murder after a young man was fatally wounded at his home.
The 23-year-old victim, who has not been named, died from a single puncture wound to his stomach, a post-mortem examination found.
Police officers and paramedics were called to his home in Elliman Avenue, Slough, Berkshire, at around 6.30pm on Tuesday.
The victim was admitted to Wexham Park Hospital where he was pronounced dead more than an hour later, Thames Valley Police said.
Four men, aged 23, 26 and two aged 30, were arrested shortly afterwards and are being held in police custody for questioning.
Three men are from the Slough area and the fourth is from west London. All four are believed to have known the victim, police disclosed.
Det Supt Rob Mason, who is leading the murder investigation, said house to house inquiries have been conducted in the area.
He appealed for anyone who has information who has not already spoken to officers to contact police as soon as possible.
The victim has not been formally identified but members of his family have been told of his death, he added.
Anyone with information is asked to contact Thames Valley Police on 0845 8 505 505, or Crimestoppers on 0800 555 111.