Production of the Oxford-AstraZeneca Covid-19 vaccine has resumed at a plant after it was suspended when a suspicious package was received.
The Wockhardt UK plant on Wrexham Industrial Estate was evacuated and the Army sent a bomb disposal unit.
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.
Both Downing Street and Wales' First Minister Mark Drakeford had been receiving updates on the incident since police were called at about 10:40 GMT.
A police cordon was put in place near the plant and the public were asked to keep away. There are no reports of any injuries.
"There are no wider concerns for public safety, however, some roads on the industrial estate will remain closed whilst we continue our investigations," North Wales Police said in a statement.
Forensic police officers were seen examining items on the road outside the plant, which remained closed after the cordon had been lifted.
Wockhardt UK said: "We can confirm that the investigation on the suspicious package received today has been concluded.
"Given that staff safety is our main priority, manufacturing was temporarily paused whilst this took place safely.
"We can now confirm that the package was made safe and staff are now being allowed back into the facility.
"This temporary suspension of manufacturing has in no way affected our production schedule and we are grateful to the authorities and experts for their swift response and resolution of the incident."
In an earlier statement, the global pharmaceutical and biotechnology company confirmed it had "partially evacuated" its site to protect staff.
The Wrexham plant has the capability to produce about 300 million doses of the vaccine a year.
Earlier on Wednesday, John Roberts, who runs CMS Wrexham Ltd, next door to the plant, said he heard a "big bang" at about 11:35 GMT - although he could not say where the noise came from.
"We're next door to Wockhardt. Three of us were talking then we heard a hell of an explosion or a bang," he said.
"I went outside, couldn't see anything. I looked the other side and two blokes were on the roof.
"The next thing the police had blocked off the road and were looking in the bushes."
His son Mark Roberts said: "The police just closed the road off and we've heard there's a bomb disposal unit.
"They've been here about an hour or so - we're on tenterhooks.
"Boris Johnson toured the factory around December time, so I wonder if that's raised the profile, as it's where they make the Oxford vaccine."
Dave Picken, 53, who lives near Wrexham Industrial Estate, said: "We've seen lots of police cars and a fire engine.
"Bomb disposal are here with a robot. We were closer to the factory but police told us to move and cordoned off a bigger area.
"I did ask an officer how big the bomb is but he said he couldn't say it's a bomb."
Visiting the plant in November, Prime Minister Boris Johnson it could provide "salvation for humanity".
Wockhardt UK entered an agreement in August to help prepare the vaccine for distribution.
When the company's contract was announced, Ravi Limaye, managing director, said: "We are immensely proud to have been selected to partner with the UK government on this project.
"We have a sophisticated sterile manufacturing facility and a highly skilled workforce."
On Thursday, Wrexham council leader Mark Pritchard said teams had worked to ensure the vaccine was not lost in the floods.
The Welsh Government said there had been "no adverse effects" on the coronavirus vaccine roll-out.