Public health experts are still trying to establish if there are any long-term risks to the people of Salisbury following the nerve agent attack on the former Russian spy Sergei Skripal and his daughter, Yulia.

During a Wiltshire council meeting on Tuesday it emerged that all areas not cordoned off in the cathedral city have been officially declared safe by the Department for Environment, Food and Rural Affairs.

All but one of the sealed-off areas are to be handed over by investigators next week, though it will be weeks or months before decontamination work is completed.

The meeting at city hall in Salisbury was told that the Skripals and two police officers were the only people being treated following exposure to the nerve agent.

Tracy Daszkiewicz, the director of public health at Wiltshire council, said there had been no “stampede of fear”. But asked by a member of the public if there were long-term implications for public health in Salisbury, she said: “That is a piece of work being looked at. At the moment we’re going with the message that it is low risk but we will update as we get more information.”

More information about the response in the first days emerged at the meeting. It was revealed that Wiltshire council staff and councillors were told not to use mobile devices after the attack because of security concerns and the government told the local authority not to give out any information.

Alistair Cunningham, the corporate director of the council and chair of the recovery coordination group, said there had been a spike in the number of people accessing its website, partly due to “not friendly” visitors trying to glean information.

During the packed meeting, it was announced that the government had put together a £1m package to help Salisbury recover.

Baroness Jane Scott of Bybrook, the leader of Wiltshire council, paid tribute to the people of the city. She said: “The community spirit has been amazing. Salisbury continues to be open for business.” But she said tourism had “taken a hit”.

Most sites could have been handed over for decontamination at the end of this week, but because the clean-up will entail teams of experts in hazmat suits returning, it was felt it was better do to it after the Easter weekend.

The meeting was told that shop takings were down across the city by 20% and by 90% in the Maltings, where the Skripals collapsed. Eight businesses remained shut and 30 in the Maltings were “severely impacted”.

One rumour – that ducks had been removed from the River Avon close to the site of the attack – was dismissed. Scott said they had simply moved because shoppers were not feeding them.

Police confirmed that a second officer had been treated as a result of the attack. A Wiltshire police spokesperson said: “We can confirm that in addition to DS Nick Bailey, another one of our police officers was treated as a result of this incident. They are receiving both full support from the force and the ongoing medical care that they require. We will not be identifying the officer or confirming any further details regarding this matter.”