Dutch police arrest a couple who fled quarantine and boarded a plane.

The Dutch military police arrested a couple on Sunday who were about to fly out of the Netherlands when they were supposed to be in quarantine. One of the pair had tested positive for the coronavirus two days earlier after arriving from South Africa, the police said.

The married couple — the husband is Spanish, the wife Portuguese — had left a quarantine hotel and boarded a plane at Amsterdam Schiphol Airport when they were arrested, according to Dutch news media. The plane was bound for Spain.

Marianne Schuurmans, a local mayor and chair of the safety region that includes the airport, told Dutch morning television on Monday that the couple was in isolation at a hospital.

Ms. Schuurmans said that the authorities didn’t anticipate that someone might break quarantine after testing positive. “We were really taken by surprise that people don’t take this seriously,” she said.

Of the roughly 600 passengers on two flights from South Africa that landed in the Netherlands on Friday morning, 61 people tested positive for the coronavirus. Those people were told by officials to quarantine in a designated hotel or at home.

After sequencing the positive tests, scientists found that at least 13 of those people had the Omicron variant, Dutch public health officials said, adding that they expected that number to grow.

Passengers from those flights — negative and positive — spent about 30 hours together on the plane and in poorly ventilated rooms at the airport, according to Stephanie Nolen, a reporter for The New York Times who was on one of the planes. While the infected passengers were told to isolate, those who tested negative were allowed to fly onward or go home, despite their exposure.