A 70-year-old man has been arrested by police investigating historic child sex abuse at a school.
The suspect, from Lancashire, was held by officers from the Kent and Essex Serious Crime Directorate on Wednesday morning.
The arrest follows three others as part of an inquiry into previously unreported alleged child sex abuse offences at Swaylands School in Penshurst, Kent, between 1967 and 1993.
The investigation follows an inquiry back in 1993 which resulted in the conviction of two men for six offences each of sexual offences against children.
A spokesman for the Kent and Essex Serious Crime Directorate said the pair were sentenced to three years for each offence, which ran concurrently, and related to four victims.
New information received by Kent Police has since resulted in a further investigation by detectives.
Since the new inquiry started, four suspects have been arrested and some 20 victims identified, located across the country and abroad.
A 72-year-old man from Norfolk, a 69-year-old man from Edinburgh and a 60-year-old man from Berkshire have all been arrested in connection and questioned by detectives.
All those suspects are on police bail, and an additional three suspects identified by officers died before the investigation was launched.
Swaylands School was set up in 1942 and between the mid-1960s and 1994 was operated and managed by the London Borough of Barnet, a police spokesman said.
Pupils aged between seven and 19 with learning, emotional and behavioural difficulties were placed there by local authorities
across London and the South East.
Detective Chief Inspector Paul Fotheringham, of the Kent and Essex Serious Crime Directorate, said: "This is a complex inquiry, where we have traced many people and records spanning a number of years.
"Kent and Essex Police take allegations of previously unreported offending seriously and every effort is made to investigate whenever appropriate and possible."