The UK's Brexit secretary David Davis is in Northern Ireland for a visit as part of the working group exploring potential future customs arrangements after the UK leaves the EU.
Mr Davis was accompanied on the visit by the Northern Ireland Secretary of State Karen Bradley and the UK's Business Secretary Greg Clarke.
They are meeting cross-border companies as part of their working group focusing on a proposed "highly-streamlined" option for addressing the unique circumstances of Northern Ireland.
The border and the potential impact of regulatory differences are central to negotiations on a pact ahead of the UK’s withdrawal from the EU next year.
British Prime Minister Theresa May has split her ministers into two teams as they work towards a reconciliation on how to manage arrangements with the EU after the exit.
One group - Brexiteers Liam Fox, Michael Gove and Remain-backing Cabinet Office minister David Lidington are considering a "customs partnership" whereby the UK would collect tariffs on behalf of the EU without the need for new border checks.
The Brexit Secretary's group will look at "maximum facilitation" - a solution based on using technology to minimise the need for customs checks after Brexit.
The maximum facilitation group is in Northern Ireland to meet representatives from the freight industry, cross-border businesses and community stakeholders to further explore how the customs model could address the unique circumstances of Northern Ireland, a statement from the Brexit Department said.
It added: "Both of the customs models currently under consideration are designed to meet the UK's three guiding principles - allowing us to trade goods and services as freely as possible with the EU, enable us to have an independent trade policy, and avoiding any hard border between Northern Ireland and Ireland while maintaining the constitutional and economic integrity of the United Kingdom."
The ministers are not expected to talk to members of the media during their visit.
Britain urged to ensure Brexit is 'green' process
Weakening environmental protections after Brexit would damage Britain's reputation internationally, the United Nations has warned.
Britain’s Environment Secretary Michael Gove has been urged by senior UN official Erik Solheim to keep his promise to deliver a "green" exit from the European Union.
Campaigners warned earlier this month that the environment and countryside will have less protection after Brexit under plans unveiled by the British government.
Mr Solheim, executive director of the UN's environment programme, said it was "incredibly important that the UK keeps the environmental standards it has had under the European Union".
In an interview with the Observer, he said: "Michael Gove promised that would happen - that there would be no reduction of standards of any sort.
"He even added that any change would be to better standards. There was a strong commitment to that from the government.
"Some of the opponents of the government had doubts about such statements, but that is the stated position from the government and it is a very good one.
"Any dilution and the UK reputation would be damaged. People in government need to make sure that does not happen. We need to make sure they have those standards or improve them, or meet the ones under the European Union."
Environmental measures from improving air and water quality to protecting endangered species are currently overseen by the European Commission and underpinned by green principles across the EU, such as "the polluter pays".
Mr Gove insisted earlier this month that new legislation would ensure environmental protections are not weakened as Britain quits the EU and a new watchdog will hold Whitehall to account for looking after landscapes and nature.
Campaigners warned that the regulator must have powers to take the government to court if it fails to deliver on green policies and raised concerns over protections for action on climate change.