WASHINGTON (NYTIMES) - The police were searching on Thursday (July 20) for six African teenagers who were reported missing from an international robotics competition in Washington. Two of them were said to have been seen crossing into Canada, law enforcement officials said.

Police officials here confirmed that two members of the robotics team from Burundi, Don Ingabire, 16, and Audrey Mwamikazi, 17, were seen entering Canada, but their destination and current location remained unknown.

It was unclear where the remaining team members were. They were identified as Aristide Irambona, 18; Nice Munezero, 17; Kevin Sabumukiza, 17; and Richard Irakoze, 18.

The six teenagers were last seen in Washington on Tuesday night near the Daughters of the American Revolution Constitution Hall, where the robotics competition took place. The team's mentor, Canesius Bindaba, reported their disappearance after he returned to the dormitories where they were staying, assuming the teenagers had taken a different shuttle bus after the closing ceremony.

It appears the students left of their own accord, event officials said in a statement. No foul play is suspected, said Aquita Brown, a spokesman for the police department.

Joe Sestak, a former Pennsylvania congressman and retired Navy admiral who is president of First Global, the nonprofit group that organised the competition, made the initial call to the police shortly after midnight, officials said. The authorities began sharing photographs and descriptions of the teenagers on missing-persons fliers on Wednesday.

The police searched Constitution Hall, interviewed other competitors in the dorms and unsuccessfully tried to reach one of the missing students' uncles, according to police reports.

The teenagers all have one-year visas, officials say.

The Burundi Embassy in Washington said in an e-mail that officials there had not known there was a team from their country in the United States until after the teenagers were reported missing.

In June, the State Department issued a travel warning for Americans going to Burundi, located between Rwanda and Tanzania, citing "political tensions, political and criminal violence, and the potential for civil unrest". The warning took note of a tenuous political situation and reported ambushes and kidnappings.

The First Global competition made international headlines after the all-girl team from Afghanistan struggled to get visas to attend the event, advertised as an international robotics Olympics. Students from more than 150 countries participated in the competition, organisers said.