The Czech Olympic Committee is opening up an investigation after five members of its delegation tested positive for COVID-19 after arriving at the Tokyo Olympics.

On Thursday, the committee announced that it was investigating whether there is a possible link between its charter flight to Tokyo and the reports of not everyone wearing a mask while on board.

According to the committee, the investigation will examine "whether all precautions against the spread of COVID-19 before, during, and after the charter flight have been complied with."

According to the Associated Press, table tennis player Pavel Sirucek, and beach volleyball players Markéta Sluková and Ondřej Perušič, have all tested positive for the virus.

The AP reported that the players and two coaches are currently quarantining at a hotel.

"The situation is serious. We have done our best to stop spreading the virus. Unfortunately, we didn’t avoid sports tragedies. I’m deeply sorry," Czech team leader Martin Doktor said in a statement.

One Czech media outlet reported that Vlastimil Voráček, one of the team doctors, was the first to test positive after the flight landed in Tokyo.

The Czech News Agency reportedthat Voráček is not vaccinated.