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Dutch border police arrested a couple on a plane after they fled a hotel where Covid-positive passengers from South African flights were staying.
One of the partners arrested was among 61 people who tested positive for Covid-19 after arriving at Amsterdam's Schiphol Airport, on board two flights from South Africa on Friday, said public health authority spokeswoman Stefanie van Waardenburg.
She said both were back in isolation, but not at the same hotel.
It was not clear whether the infected person was among the 13 passengers found to have the Omicron variant that has prompted travel restrictions around the world after being reported by health officials in South Africa last week.
Police spokesman Stan Verberkt said the couple were a Spanish man, 30, and a Portuguese woman, 28.
"The Royal Netherlands Marechaussee at Schiphol arrested a couple this evening who had fled from a quarantine hotel," Mr Verberkt said.
"The arrests took place on a plane that was about to take off. They were on a plane that was about to depart for Spain at about 6pm."
Border police are now laying charges against the couple for jeopardising public safety, he said.
It was not clear how the couple left the hotel or how the alarm was raised.
The Dutch authorities announced stricter new travel protocols on Friday as alarm mounted around the world about the new Omicron variant.
The 600 people on the two South Africa flights on Friday spent most of the day stuck at the airport being tested in conditions that one person described as "dystopia central".
Dutch Health Minister Hugo de Jonge had said only hours earlier that authorities in the Netherlands would ensure that people obeyed quarantine rules.
The Covid-positive passengers from the South Africa flights are almost all at the hotel while a handful have been allowed to go into home quarantine. Passengers who tested negative have also been ordered into home quarantine.
"We will control whether they keep to those rules," Mr de Jonge told reporters.
The health minister added that it could not be excluded that more people than the initial 13 had contracted the Omicron variant.
"We are concerned, but how much we should be at this stage we don't know yet," Mr de Jonge said.
Police and security guards were on guard at the quarantine hotel, a spokeswoman for the local mayor said earlier.
"The security is there for a reason," she said.