Neighbours have told of the drama that unfolded on their street, as police continued to search a house where firearms and chemicals were recovered.
Meanwhile, three people arrested on suspicion of firearms offences were released on bail.
Norfolk police said officers were "conducting routine enquiries" at a property on Milton Avenue, King's Lynn on Saturday morning.
The force said they "had reason to conduct a search, recovering a quantity of firearms and some chemicals".
Neighbours living on the cul-de-sac, near the College of West Anglia, said they saw four fire engines and large numbers of police at the scene.
On Monday forensic officers wearing protective suits could be seen going in and out of the property, while items were still being removed and loaded into a large van.
Norfolk police said in a statement: "The chemicals have since been examined by Norfolk Fire and Rescue Service, along with officers from Norfolk police. It has since been established they are not a cause for concern and no longer form part of the investigation.
"One man in his 50s, a second man in his 20s and a woman in her 20s, who were arrested on suspicion of firearms offences, have been released on police bail pending further enquires. A cordon remains on the property whilst enquiries are ongoing."
Curtains and blinds at the two-storey semi were closed as a number of officers worked inside in the house. Police have not said how many firearms were recovered, or what type of weapons were found.
One neighbour said: "It's very quiet down here normally. I saw all the fire engines and police, someone said it was something to do with firearms and fuel or chemicals."
Another added: "It's been a bit mad, there were four fire engines down here, loads of police and forensic people."
People living near the property said they did not know the people who lived in it. One said they sometimes saw a young woman going in and out of the house.
Anyone with information should contact Swaffham CID at Norfolk Constabulary on 101 quoting reference number 159 of 10 July 2021.
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