Sydney Mimer, 77, died on March 26 at HMP Littlehey where he was serving an 18-year prison sentence.
In the mid-2000s Mimer had carried out attacks on a girl aged seven to nine at the time at an address in Poplar and in a vehicle he owned.
The abuse came to light in 2016 when the girl confided what had happened to her mother.
When he was jailed Det Con Neil Golding described Mimer as a “predatory paedophile”.
He also said he suspected Mimer may have carried out other offences.
“We are appealing to anyone who has been targeted by Sydney Mimer to come forward and speak to the police,” Det Con Golding said.
Mimer denied the charges when his trial opened—then halfway through his trial he pleaded guilty to two charges of raping a child under 13, one charge of sexual activity with a child under 13 and two of causing a child under 13 to engage in sexual activity.
The Prisons & Probation Ombudsman is investigating his death at the Cambridgeshire prison.
