The ban will be effective for an initial for an initial five days from January 22nd, the transport ministry said in a statement.

The decision is related to suspicions regarding “irregularities with tests in Dubai,” the ministry said.

Flights would therefore be banned for five days “until it has been possible to investigate this issue to the bottom and ensure that the required negative tests are actual negative tests which have been taken properly,” transport minister Benny Engelbrecht said in the statement.

“We have previously seen mutations come in via Dubai and we cannot ignore a suspicion like this,” the minister also said, referencing a previous detection in Denmark of a mutation first reported in South Africa. The person in whom the mutation was detected had travelled to Denmark via Dubai.

Under current rules, everyone travelling to Denmark by air must provide a negative Covid-19 test no more than 24 hours old when boarding flights.

READ ALSO: These are Denmark's entry rules for negative Covid-19 tests

A report made to the foreign ministry resulted in the decision to implement the ban, the transport ministry said in the statement.

Engelbrecht elaborated on the mention of a whistleblower in comments to national broadcaster DR.

“There was a specific and serious report filed by a citizen in relation to how tests are conducted at entrances in Dubai and we must therefore ensure there are no problems with this,” he said.

“It is no use us having Danes or others who fly from Dubai who might be positive or infected with Covid-19 or maybe a mutation like the South African one,” he continued.

Danish authorities needed to ensure tests were not carried out “sloppily or intentionally incorrectly,” Engelbrecht said.