The latest arrest was of a 23-year-old man in Sussex. Britain has lowered its security level from "critical" to "severe," meaning the country remains on high alert a week after the suicide attack killed 22 at a concert in the northern English city.
British police on Monday said they had arrested a 16th person in connection with their investigation into the Manchester suicide bombing last week.
They arrested the 23-year-old man in Shoreham-by-Sea, Sussex "on suspicion on offences contrary to the terrorism act," Greater Manchester Police said.
Of those arrested in Britain in connection with the attack in which 22 people died, 14 men remain in custody for questioning, the police said. Two have been released.
The attack on May 22 was Britain's worst in more than a decade. British extremist Salman Abedi detonated a powerful bomb in a suicide attack at a concert by US singer Ariane Grande.
Several of the victims were children, the youngest being just eight. Scores were injured.
Daesh claimed responsibility for the attack. Police have been hunting for a network of people connected to Abedi. Britain's Interior Minister Amber Rudd on Sunday said there were "potentially" still members of the cell at large.
Abedi's brother and father are being held in Libya.
On Sunday, police released photographs from security cameras showing Abedi on the night of the massacre, wearing jeans and trainers, a black body warmer and a baseball cap, with the straps of his backpack visible on his shoulders.
The northern English city is slowly returning to normal, with sporting events held over the weekend under tight security.
Britain has downgraded its national security level from its highest level. But it still remains at "severe", meaning an attack is highly likely.
Britain's MI5 Security Service has started an internal review on whether there are lessons to be learned from its handling of intelligence on Abedi's attack.
"This is a review that would seek to answer whether there are lessons to be learned from how the Security Service handled the intelligence on Abedi," the source, who spoke on condition of anonymity, told Reuters.
Before he carried out the attack, Abedi, a Muslim whose parents were from Libya, was one of 20,000 people who was known to MI5 but not one of the 3,000 people who are under active investigation, according to the source.