Mid and East Antrim Council said its staff will return to work after having been withdrawn as a result of safety concerns.
A spokesperson for the council said: “Mid and East Antrim Borough Council staff will return to their inspection duties at Larne Port this evening following the completion of a PSNI [Police Service of Northern Ireland] threat assessment and subsequent risk assessment by the council.
“The health and safety of our staff remains our top priority.”
Border staff were withdrawn from Larne and Belfast ports after threatening graffiti appeared, referring to port workers as targets.
Staff also reported signs of suspicious behaviour, including people writing down vehicle licence plate numbers.
Inspectors employed by Stormont’s Department of Agriculture, Environment and Rural Affairs were also withdrawn from duties on Monday, but the department has not yet made a decision about their return.
A spokesperson said: “The department has received the findings of the formal threat assessment from the PSNI and is currently considering it alongside its own internal risk assessment.
“Any decision to recommence full checks will be informed by both documents.”
The PSNI said loyalist paramilitaries were not involved in the threats made to workers carrying out the post-Brexit border checks. Instead, disgruntled individuals or small groups may have been responsible, the force said.
In a statement, 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.”
The Democratic Unionist Party, which has vowed to scrap the Northern Ireland protocol that keeps the Irish land border open in line with EU regulations, rejected claims it was whipping up tensions over Irish Sea trade.
The first minister, Arlene Foster, said it was “absolutely ridiculous” to suggest that her party was stoking tensions around the disruption to trade for political reasons.
The withdrawal of border staff came after shortages of certain fresh foods in supermarkets at the start of the year following the end of the Brexit transition period, and after some businesses based elsewhere in Britain found themselves poorly prepared for the additional paperwork required to ship goods to Northern Ireland.
On Friday, Ms Foster said the UK government must take “affirmative action” after more than 100,000 people signed her petition to parliament calling for the removal of “any impediment or barrier to unfettered trade within the United Kingdom”.
She said: “We have made the case to the prime minister and now the people have made a very public appeal to the government of their country to act.
“This is not the time for more words and drawn-out processes. This is the time for affirmative action to ensure that there is an unfettered flow of goods within the UK single market.”
Additional reporting by agencies
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