The bodies of four people, including a man and woman in their 30s, an 11-year-old girl and a three-year-old boy, have been found in a flat in west London.
Metropolitan Police were called at 3.12pm on Friday to concerns for the welfare of the occupants of a house in Staines Road, Bedfont, Hounslow.
Officers forced entry to the property and tragically found the bodies of four people inside the house.
It is believed all four people were related but enquiries are underway to carry out formal identification and inform their next of kin.
A neighbour has said the incident in Bedfont involved a family who were "normal neighbours".
Just one police officer was stood with his arms folded outside the property on Saturday morning.
A man who lives next door, who did not wish to be named, told reporters: "They were just normal neighbours- we just had greetings here and there, that kind of stuff.
"I came home from work and there were police everywhere. It was really busy. Nothing like that happens here.
"I have no idea what happened."
As forensic investigators arrived at the house in Hounslow this morning, they could be seen gathered around the entrance to the building, with some wearing face masks and gloves.
Naresh Regmi, 49, who lives nearby, said: "The police were here yesterday with forensics, working on the property.
"We didn't know the people who lived there – maybe they were new to this area?"
A woman, who laid flowers at the scene in Hounslow, said the family who lived in the house were eastern European and "kept themselves to themselves".
Michelle Cunningham, 49, who lives nearby, said: "I thought I'd come and lay down flowers after hearing what happened. It's so sad.
"They were an eastern European family, kept themselves to themselves. I used to see the man outside his house sometimes.
"I didn't know their names or much about what happened - I just heard about it last night."
The Met's investigation is led by homicide detectives from Specialist Crime.
Chief Superintendent Sean Wilson, local policing commander in west London, said: "Our investigation is at a very early stage, and based on our initial enquiries, we are not currently seeking anybody else in connection with the incident.
"I know the shock and distress that this terrible incident will cause among the community in Hounslow and beyond. I can assure local people that specialist officers are working to establish exactly what happened and I will provide further information as soon as I can.
"I am also aware that this incident will be particularly upsetting for children, and I ask people to please be responsible about what they post on social media, including not naming or speculating as to the names of those who’ve died.
"There will be additional police officers in the area across the weekend, I urge anyone with information or concerns to speak with those officers."
Enquiries are ongoing.
Anyone with information that may assist the investigation is asked to call 101, quoting reference 5135/16Jun.
