Dutch health authorities said that 61 people who arrived in Amsterdam on two flights from South Africa on Friday tested positive for Covid-19, and they were conducting further testing early Saturday to see if any of the infections are with the recently discovered omicron coronavirus variant.

Around 600 passengers arrived at Amsterdam’s Schiphol Airport on the two KLM flights on Friday and then faced hours of delays and testing due to concerns over the new virus variant.

The Dutch health ministry said early Saturday 61 tests had come back positive.

“Travelers with a positive test result will be placed in isolation at a hotel at or near Schiphol,” health authorities said in a statement.

“Of the positive test results, we are researching as quickly as possible whether they are the new variant of concern, now named ‘Omicron.'”

The Dutch government banned all air travel from southern Africa early on Friday. Health Minister Hugo de Jonge determined that passengers already en route to the Netherlands would have to undergo testing and quarantine upon arrival.

Passengers on the two KLM flights, from Cape Town and Johannesburg, said they were kept waiting on the tarmac for hours.

“Vigorous applause because there is a BUS that has come to take us … somewhere,” tweeted New York Times journalist Stephanie Nolen, a passenger on the flight from Johannesburg who later said she had tested negative.

“Bus to a hall to a huge queue. I can see Covid testers in bright blue PPE far on the distance. Still no snacks for the sad babies,” she added in a second tweet.

A spokesperson for the health authorities in Kennemerland, the Dutch region that oversees Schiphol, said the positive cases were being analyzed by an academic medical hospital to determine whether they are the new strain.

The new variant has been detected just as many European countries are grappling with a surge in coronavirus cases.

The Dutch government separately on Friday announced the nighttime closure of bars, restaurants and most stores as it tries to curb a record-breaking wave of COVID-19 cases that is swamping its healthcare system.