The names of two policemen suspected of child pornography were sent to the force involved in the Soham murder inquiry before they were assigned to the case.
It has been revealed that Cambridgeshire police had the men's names for a month before the girls disappeared but the list wasn't checked until last week.
Detective Constable Brian Stevens (41) was a liaison officer for the family of Jessica Chapman, and Pc Antony Goodridge (34) was an exhibits officer.
A month before Jessica and her friend Holly Wells disappeared Cambridgeshire police received a list of suspects, including the two officers, from police investigating an alleged Internet pornography ring.
A police source said: "As soon as the names of the officers were identified an operation was put in place and arrests were carried out in a day."
On July 5th, Cambridgeshire police was given the list of 279 names and addresses of people in the county allegedly identified by the US authorities as using pay-per-view child pornography websites.
Cambridgeshire officers met after the list was received and it was decided a full team should be set up to investigate the names and it was agreed to meet again on August 5, it is understood.
The list had been passed to the force by the National Criminal Intelligence Service by the US authorities. But the girls disappeared on August 4th so the meeting was postponed.
The list was finally examined last week. When the names of the officers were spotted, detectives from West Midlands Police were immediately called in and they were arrested early the following day.
Stevens has been charged with three counts of making and inciting the distribution of indecent pseudo-photographs of children. Goodridge has been charged with four counts, of making, possessing and inciting the distribution of indecent pseudo-photographs of children. The officers were granted conditional bail at a court hearing yesterday and are due to appear in court again on November 11th.
PA