Detectives were questioning a woman today after firefighters found a body after a suspicious fire engulfed a house.
A 27-year-old woman was found dead in a ground-floor room at the property in Lake Gardens, Dagenham.
Firefighters wearing breathing equipment used ladders to rescue a man and two children from a first-floor bedroom at about 1am today.
All three were taken to an east London hospital for treatment after suffering smoke inhalation.
Metropolitan Police launched an inquiry and said the blaze was being treated as suspicious.
A spokesman said a 20-year-old woman was arrested and was being questioned today.
He added: "A 27-year-old woman was found inside the premises. She was pronounced dead at the scene at 1.18am.
"Police believe they know her identity and are in the process of informing next of kin. We await formal identification.
"A post-mortem examination will be scheduled in due course."
A London Fire Brigade spokesman said four fire engines and about 20 firefighters attended the blaze.