Loyalist paramilitaries are not involved in threats made to workers conducting post-Brexit trade checks at Northern Ireland’s ports, police have said.
Disgruntled individuals or small groups may be responsible, rather than the organised gangs that once instigated serious violence.
Inspections of goods arriving at Larne and Belfast ports were suspended on Monday and officials withdrawn after sinister graffiti and reports of intelligence-gathering on inspectors.
The European Commission said Brussels’ representatives were also being temporarily withdrawn from duties at the ports.
The Police Service of Northern Ireland (PSNI) is stepping up patrols near the ports.
Assistant Chief Constable Mark McEwan said: “We are concerned about the actions of a number of individuals and small groups.
“We don’t believe that those actions are organised. But they do give us cause for concern.”
Loyalists are angry at what they see as the imposition of a new economic frontier with the rest of the UK due to the Northern Ireland Protocol keeping the Irish land border open.
Lorries arriving at new inspection facilities at Belfast Port on Tuesday morning were turned around and redirected by Border Force officials.
Mr McEwan told the PA news agency: “We are aware of a single anonymous piece of information that has been circulating and that has caused real concern to staff and to their employers.
“We were able to share with partners our assessment today that there is absolutely no information to substantiate or corroborate the claims made that paramilitary organisations are involved or behind threats or intimidation to staff at points of entry.”
Mr McEwan said recent weeks had seen increased “tensions and discontent” within the community in relation to the protocol.
He added: “We believe this is the actions of individuals and small groups involved in spraying graffiti and other low-level types of incidents that has resulted in staff feeling threatened and intimidated and that’s what has led us to this point.”
Ports staff have expressed concerns that individuals had been spotted taking down number plate details.
Stormont’s Department of Agriculture, the Environment and Rural Affairs (DAERA) officials left while 12 local council workers also pulled out of Larne on Monday following an “upsurge in sinister and menacing behaviour in recent weeks”.
Political parties in Belfast are sharply divided on EU withdrawal and the protocol, which keeps the land border in Ireland open but imposes controls on the Irish Sea.
Stormont Executive ministers united on Tuesday.
They said: “As public servants, these staff should be allowed to do their jobs without fear and it is unacceptable and intolerable that threats have been made.”
Unionists have urged the British Government to override parts of the protocol, which they fear endangers trade between Northern Ireland and the rest of the UK, its biggest market and supplier of goods.
Hauliers experienced problems shipping goods into Northern Ireland from Great Britain, some parcel deliveries were halted and supermarket shelves temporarily developed gaps last month, although some red tape issues have been resolved.
Michael Gove told the Commons: “Trust has been eroded, damage has been done and urgent action is therefore needed.”
The Cabinet minister added that a three-month light-touch regulation grace period for supermarkets following the end of the Brexit transition should be extended.
“We do need to make sure that supermarkets and other traders can continue, as they are at the moment, to be able to supply consumers with the goods that they need.”
Taoiseach Micheal Martin said it was a “sinister and ugly” development.
The European Commission swiftly backtracked last week after facing intense criticism for attempting to hinder the free flow of movement across the Irish border in respect of coronavirus vaccines, using a legal clause called Article 16.
Mr Gove said: “Not only plans to stop vaccines being delivered through legally-binding contracts at the height of a pandemic, but also – and critically – a unilateral suspension of the painstakingly designed and carefully negotiated provisions of the protocol, which the EU has always maintained was critical to safeguarding the gains of the Northern Ireland peace process.”