The Charity Commission has revealed that it has been pursuing a statutory inquiry into the Essex Islamic Academy, where the religious teacher Umar Ahmed Haque tried to radicalise children.
Haque was convicted at London's Old Bailey on Friday of preparing acts of terrorism. He will be sentenced this month.
The court heard that he came into contact with up to 100 children as young as 11 at the academy, also known as Ripple Road Mosque, in the London borough of Barking.
He pleaded guilty to disseminating terrorist material to children.
After Haque’s conviction, the commission issued a statement saying it had begun a statutory inquiry in October last year.
"The commission did not previously make the opening of the inquiry or its prior regulatory engagement with the charity public to avoid prejudicing the police investigation and subsequent criminal trial," it said.
"Now the criminal proceedings are over, the regulator will resume its investigation in full."
The commission said it would consider "how Mr Haque was able to attempt to radicalise children, and what the trustees and others at the charity knew about this.
"The regulator will examine the level of supervision, due diligence and oversight the charity had over Mr Haque, and its adherence to safeguarding policies and procedures."
The commission added that it had spoken to police, educational regulators and the local authority and "will deal with any failings or evidence of misconduct or mismanagement by taking appropriate regulatory action".
In January, the commission ordered the trustees to stop educational classes and recreational activities that involved under-18s.
The regulator said this order would apply "until the trustees are able to demonstrate that they have complied with a number of urgent actions".
Michelle Russell, director of investigations, monitoring and enforcement at the commission, said: "This is one of the worst cases we have seen, with children as young as 11 being exposed to harm through attempted radicalisation and terrorist material by this man.
"We will continue to work closely with the police and other authorities to tackle the threat terrorism and extremism poses to charities, their beneficiaries and their work."
Essex Islamic Academy said in a statement that it "utterly condemned the activity of Umar Ahmed Haque".
It said it had appointed an affected parent on its board "to help guide us in our effective response towards the families involved".
It added: "We have strengthened and improved further our governance since the incident."
Another Islamic educational charity probed
The regulator also announced on Friday that it had opened an inquiry into the Islamic educational charity the Lantern of Knowledge Educational Trust because of concerns about its administration, governance, management and safeguarding.