A man has been arrested after a suspicious package was sent to a Covid-19 vaccine factory in Wrexham.
On Wednesday the Wockhardt UK plant on Wrexham Industrial Estate was evacuated and the Army sent a bomb disposal unit.
Kent Police said a 53-year-old man from Chatham had been arrested on suspicion of sending the package and remains in custody as inquiries continue.
It said warrants had taken place on Luton Road and Chatham Hill, Chatham, on Thursday morning.
There is no evidence to suggest there is an ongoing threat, it added.
On Wednesday police said the package had been made safe and its contents would be "taken away for analysis".
Wockhardt said staff had been allowed to return and its production schedule had not been affected.
The company entered an agreement in August to help prepare the vaccine for distribution.
The plant has the capability to produce about 300 million doses of the vaccine a year.
On a visit to the factory at the end of last year, Prime Minister Boris Johnson said it could provide "salvation for humanity".