A teenager has been arrested in Hertfordshire after a mass email bomb hoax targeting schools across the country – including in Stevenage, St Albans and Sandy.

The National Crime Agency confirmed last night that a 19-year-old man had been arrested in Watford following the hoax, which saw 24,000 threatening emails sent to schools and colleges – according to national media reports, because of a feud between rival Minecraft gamers.

A National Crime Agency spokesman said last night: “Hertfordshire police officers, working as part of an NCA-led investigation, arrested a 19-year-old man in Watford today on suspicion of blackmail and making malicious communications relating to the hoax bomb threat that closed hundreds of UK schools this week.

“We understand parents’ and teachers’ concerns but stress there was no credible threat to the emails schools received. However we are taking the communications extremely seriously.

“As this is now a live investigation we are unable to comment further.”

The email threat was sent to eight schools in Hertfordshire – The Valley School in Stevenage, Abbot’s Hill School in Hemel Hempstead, Hertford’s The Sele School, Duncombe School and Richard Hale School, Stanborough School in Watford, St Albans High School For Girls and Samuel Ryder Academy, also in St Albans.

In Bedfordshire, Sandy Upper School, Fairfield Park Lower in Fairfield, Roecroft School and Pippin Pre-School – the latter two based on the same Stotfold site – all decided to temporarily evacuate when they received a hoax email about a bomb.

The exact number of local schools affected is not clear, as local authorities could only account for ones under its jurisdiction, and not academies and independent schools.

Bedfordshire Police had advised schools on Monday that evacuation was not necessary, but some schools still decided to send children home.