A 30-year-old man has been arrested on suspicion of murder after the bodies of a woman and two children were discovered in a flat.
Merseyside Police launched an investigation after being called to a ground-floor flat in Falkner Street, Toxteth, at around 7.30pm after concern for the safety of the occupants.
Officers said the investigation was in its early stages, but believe it is "domestic related".
They added police were not looking for anyone else at this stage.
The arrested man has been taken to hospital after falling ill and police said a post mortem will be carried out to establish the cause of death of the deceased.
Anyone with information is asked to call police on 0151 777 4065 or Crimestoppers anonymously on 0800 555 111.
People in Falkner Street had been evacuated from their homes earlier on Tuesday evening over concerns about a fuel leak.
Police closed the street and urged people in neighbouring roads to remain indoors and keep windows closed.