Four police officers' conduct is being investigated as part of an inquiry into failures to alert forces to paedophiles like jailed doctor Myles Bradbury.
Bradbury, from Cambridge, was jailed for 22 years for sexual assaults on child patients.
The four officers worked for the police's national Child Exploitation and Online Protection Centre (CEOP).
The notices were served as part of an Independent Police Complaints Commission investigation.
CEOP was criticised because it had been given information about Bradbury and other suspected paedophiles by police in Toronto, Canada in July 2012.
A BBC investigation found the information was not passed on for 16 months.
The information was disseminated when the National Crime Agency took over CEOP in November 2013 and Bradbury was arrested a month later.
Bradbury, 41, of Herringswell in Suffolk, carried out his offences while working at Addenbrooke's Hospital in Cambridge between 2009 and 2013.
There were 18 victims of sexual abuse and he was also found with 16,000 indecent images of children.
The IPCC said the four officers had held management roles in CEOP and the gross misconduct notices served on them, indicating their conduct was under investigation and no conclusions have yet been reached.
An IPCC spokesman said: "Two of the officers have retired since the incident, one officer remains at the NCA and one officer who was on secondment from Lincolnshire Police has since returned there.
"All four notices are for failing to adequately progress and manage the referral by Toronto Police from Project Spade.
"The investigation remains ongoing."
The Canadian police passed on information about 2,345 British suspects in 2012.
The list also included Martin Goldberg, the deputy head of Thorpe Hall School in Southend, who had images of children undressing in changing rooms in his possession.
He was found dead the day after being interviewed by police.