An 18-year-old man was arrested in Abbots Langley last night on suspicion of making "malicious threats" to schools.
The National Crime Agency has said the incident is being linked to the hoax bomb threats which closed more than 400 schools last week - including six in Hertfordshire.
A 19-year-old man was arrested in Watford by Hertfordshire police officers after emails were sent to schools threatening to bomb grounds if money was not handed over.
Yesterday Hertfordshire Police confirmed they were responding to reports of "malicious" emails sent to schools across the country.
It is not known which schools were affected.
A statement from the National Crime Agency read: "On the evening of Wednesday March 28, NCA and Hertfordshire Police officers arrested an 18-year-old man in the Abbots Langley area on suspicion of making malicious communications relating to the threatening emails received earlier by a large number of schools and colleges throughout the UK.
"We understand these threats have caused considerable concern to the public but we do not assess there to be an increased risk to the public.
"We believe this incident is linked to the hoax bomb threats that closed hundreds of UK schools last week.
"As this is a live investigation we are unable to comment further."
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