An 18-year-old youth has been arrested over bomb threats sent to hundreds of schools in Britain and the United States in March, the National Crime Agency (NCA) said on Thursday.
The calls, which resulted in many schools being evacuated, demanded money and threatened to detonate explosives.
The teenager was the third 18-year-old in Britain to be detained in connection with the threats. He was held on Wednesday on suspicion of making threats to kill, blackmail and malicious communications.
The arrest was made at his family home in Hampshire, southern England, police said.
“We believe those arrested so far are all part of the same group,” said NCA senior investigating officer Marc Horsfall in a statement.
The investigation continues.