Hordes of teenagers displaying colors and flags from 157 countries cheered wildly in DAR Constitution Hall on Tuesday afternoon, exhausted and exhilarated from two days of robotics competitions. Somewhere on the packed auditorium floor, six teenagers from Burundi quietly slipped away amid the closing gala.

D.C. police said the 16 to 18 year olds from the small African country were long gone by the time their chaperone reported them missing early Wednesday and police later posted their photos on the Internet . By Thursday morning, police said Don Charu Ingabire, 16, and Audrey Mwamikazi, 17, were in Canada with friends or family and the other four were somewhere in the U.S., not yet with relatives but believed to be safe.

How and why the students or others orchestrated what appears to authorities a well-planned but very secret bid for possible asylum in Canada and the U.S. remains a mystery. Neither the students nor their relatives could be reached, and the organizer of the competition and a representative of the Burundi Embassy called their disappearance a surprise.

[Two of six missing African teens cross boarder into Canada]

The FIRST Global Challenge robotics competition is run by Joe Sestak, a former Navy admiral and congressman. A statement from his spokesman, Jose Escotto, said the group “may have self-initiated the disappearance,” noting that the students had taken their clothes from their dorm at Trinity Washington University and left their room keys behind.

The Burundi robotics team are shown, in the screengrab from First Global Media video, at the First Global competition in Washington, DC. The team has disappeared after the competition. (N/A/FIRST Global Media )

The statement says the coach, Canesius Bindaba, left Constitution Hall Tuesday evening without the teens, assuming they had returned to the dorm on a different shuttle bus and only later discovered they were gone. After a search, Sestak called police shortly after midnight Wednesday. The statement said there was security at the dorms and to shuttle the students to events.

Speaking over WhatsApp from Kenya, a stop on his trip home, Bindaba said he had heard rumors that the teens might have plans to stay in the U.S., but he hoped they were not true. “I just tried to build some kind of trust, hoping they were just rumors,” he said. “I feel cheated and disappointed by those who planned this behind my back.”

In addition to Ingabire and Mwamikazi, Richard Irakoze, 18, Kevin Sabumukiza, 17, Nice Munezero, 17 and Aristide Irambona, 18, also were reported missing. Youth at the competition, won by Team Europe, built robots that sorted blue and orange balls — meant to simulate clean and contaminated water.

Burundi Embassy’s First Counselor Benjamin Manirakiza said his office did not know the six students were in the U.S. until Bindaba informed him they had disappeared.

“We want to make sure the team members are in safe hands,” Manirakiza said in an interview. “That is our wish.” But, he added, “I am surprised the entire team left.. . . I don’t know if they planned this or maybe had some relatives help. Many people from Burundi come to the U.S. for conferences, but they go home.”

The robotics competition had run into a problem even before the Burundi team left when a team from Afghanistan was initially barred from getting visas. U.S. officials are wary of approving visa requests to some groups of scholarship students, academic fellows and teachers, afraid they might not return home.

[U.S. wary of granting Visas to some academic groups fearing they won’t go home]

Burundi has been roiled by civil war and reports of human rights abuses. In 2015, Burundi’s president, the former Hutu rebel leader Pierre Nkurunziza, successfully sought reelection to a third term. Mass protests organized by the opposition were put down, and the climate grew more repressive after an attempted coup in May 2015. The State Department issued a travel warning in June, advising Americans of “political tensions, political and criminal violence, and the potential for civil unrest.”

That warning stated that rebel forces, ex-combatants and youth gangs from Congo had reportedly attacked and kidnapped civilians, while armed groups have ambushed vehicles. Hundreds of people have been killed, and hundreds more have disappeared, allegedly the work of Burundi’s security forces. In the past two years, more than 400,000 people have fled the country, according to human rights activists.

[Global competition starts for international robotics teams]

Pat Jones, the executive director of immigrant outreach services, a nonprofit based at St. Matthew Catholic Church in Baltimore, called the Burundi students brave and said their families could face persecution if they knew or helped the teens flee. She said it is difficult for a Burundi to obtain a Visa to the U.S. and there are worries within the struggling country about talented people leaving and creating a “brain-drain.”

“Maybe they were coached in some way,” said Jones, whose group helps people from more than 140 countries seek asylum or other help. “Or perhaps they knew of family here and leaving made sense. I think it would have to be pretty well coordinated.”

Bindaba said he was proud of bringing the Burundian team to an international stage. “My dream was to achieve something no one has done before in my country,” he wrote over WhatsApp. “To come up with the first robot build by Burundian kids was a sign of hope to me and my beloved country as well.”

Carol Morello, Robert McCartney, Tara Bahrampour and Clarence Williams contributed to this report.