The 37-year-old and two girls aged 13 were found at a property in Grove Road, Chadwell Heath at 13:10 BST on Tuesday.
Shighi Kotuvala and sisters Niya and Neha Rethishkumar had not been seen since Sunday.
Their father, Pullarkattil Rethish Kumar, 44, who was missing from the address, was found hanging at Woodford Reservoir in Walthamstow.
Formal identification is yet to take place.
Post-mortem examinations are due to take place later, but Scotland Yard said the three female bodies had no signs of visible injuries.
The family's neighbour, Zoya Habibani, 24, described the family as "really friendly" and garage owner Bobby Singh, 41, said they were "very reserved" and "polite".
He said: "I hope someone finds out the answers. I hope they rest in peace as well."
The Metropolitan Police said it was initially called to the property on Monday night after concerns were raised about the family's welfare.
There was no response or signs of a disturbance at the house so the officers left.
They returned on Tuesday and broke into the property and found the bodies of the woman and the two girls.
Det Supt Kenny McDonald said: "At this stage in our ongoing investigation we are not looking for anyone else in connection with the deaths.
"We are making extensive enquiries to trace next of kin, who we believe to be outside of the UK."
The Met said as part of its "routine" it had referred its response to the Directorate of Professional Standards and the Independent Police Complaints Commission.
A mother and her twin daughters have been found dead at a house in east London, police have said.