The big controversy leading up to the FIRST Global international robotics competition in Washington was whether a team of girls from Afghanistan would be able to participate, after their initial visa applications were denied.

As it turned out, the Afghan girls got into the country, after direct intervention from President Donald Trump, and competed without incident.

Instead, it was a team from Burundi that created an immigration-related uproar after it disappeared in what appeared to be an effort to avoid returning to their home country.

The disappearance of the six Burundi teenagers, four boys and two girls, from the competition is casting a spotlight on the visa process used to admit competitors.

Police in Washington DC are continuing to investigate the disappearance, which was reported on July 19, the day after the robotics competition ended.

Two of the six teens were seen crossing the border into Canada, police said.

Event organisers believe the youths may have planned their disappearance, and members of the Burundi-American community say there is little doubt they are planning to seek asylum, either in the United States or in Canada.

The robotics team's coach, Canesius Bindaba, told The Washington Post that he had heard rumours the teens might be planning to stay in the United States, which he hoped were not true.

"I just tried to build some kind of trust, hoping they were just rumours," he said.

The Burundi robotics team, from top left, Richard Irakoze, Kevin Sabumukiza, Nice Munezero, Aristide Irambona, Don Ingabire, and Audrey Mwamikazi. ( AP: Washington Metropolitan Police Department )

Police reports indicate that the Burundians were in the country on travel visas valid for one year, although immigration law experts said Customs and Border Patrol agents would have limited the stay to a certain number of days when the team arrived.

William Cocks, spokesman for the State Department's Division of Consular Affairs, said the State Department screens visa applications, and one of its goals is to ensure that visa applicants are not trying to use a tourist visa to permanently immigrate into the US.

He declined to discuss the Burundi teenagers' specific situation.

A spokesman for Customs and Border Protection also declined comment.

The competition, designed to encourage youths to pursue careers in math and science, attracted teams of teenagers from more than 150 nations.

AP