Two women have been found dead and a man seriously hurt at a house in West Sussex.
The women's bodies were discovered outside the property in Hazel Way, Crawley Down, while the man was found inside by police at 10:20 GMT.
Police said the injured man had been arrested on suspicion of murder.
Earlier reports suggested a knife was used in the attack, but Sussex Police have since said "this is not a knife crime".
The force gave no further details about the cause of death. The injured man has been taken to Royal Sussex County Hospital in Brighton.
Det Ch Insp Alex Geldart said: "This is a fast-moving investigation which will see significant police resources deployed to the scene for the foreseeable future.
"We are grateful for the support and patience of the local community while we conduct our inquiries.
"My thoughts are very much with the friends and family of the two women who have sadly lost their lives."
The detective said it was an isolated attack with no risk to the public and added: "In response to media speculation I wish to make it absolutely clear that this is not a knife crime."
Three forensic tents were pitched in the street and forensic investigators could be seen combing the area for evidence.
A cordon is in place around the houses close to where the bodies were found.
Anyone with information is asked to report online or call 101, quoting Operation Deanland, or ring Crimestoppers.