Police are searching for six African teenagers, who were reported missing from their rooms Tuesday night at an international Robotics Competition in Washington, DC. The teenagers are part of the Burundi robotics team and were reported missing by their coach.

Two of the teenagers were seen crossing the Canadian border, authorities said. The location of the other four are unknown, but foul play is not suspected, authorities told USA TODAY.

Team Burundi

Team Burundi is comprised of two 17-year-old girls, one 16-year-old boy, and three 18-year-old boys, NBC News reported.

All six students have one-year visas for the US, USA TODAY reported. The team's slogan, according to FIRST Global's website, is "Ugushaka Nugushobora," which means "where there is willing is also the ability."

The Burundi coach reported his students' absence to the competition organizers Tuesday night, NBC News said. FIRST Global's president, Joe Sestak, reported the missing teenagers to police.

The competition was held at Constitution Hall and students stayed at Trinity Washington University. Buses were provided to transport students between the two locations. Team Burundi's coach discovered they were missing after trying to meet up with them after closing ceremonies on Tuesday. He assumed they had taken a different bus back to the University.

The students packed their belongings and left their dorm keys in their coach's bag, The New York Times reported.

The Burundi Embassy in Washington, DC did not know the students were in the US until they were reported missing after midnight on Tuesday, NBC said. On Thursday the Embassy said it was not obligated to check in on Team Burundi.

The US Department of State issued a travel warning last month on growing political violence and civil unrest in Burundi.

FIRST Global Challenge

The FIRST Global Challenge robotics competition drew attention earlier this month when a team of Afghan girls were denied entry to the US twice. President Donald Trump intervened to approve their visas, and they arrived in the US on Saturday.

Trump's daughter, Ivanka, attended the event on Tuesday.

High school students from almost 160 nations competed in Washington, DC for the first annual competition to encourage global youth to engage in science, technology, engineering, and mathematics, according to the FIRST Global website. The three-day competition's goal was to improve access to clean water through cooperation and "engineering tasks such as the storing of drinkable water, filtering of contaminated water, and procuring of new sources [of] water."