Six teenagers who were members of an African robotics team competing in Washington, D.C., this week disappeared, with two of the teens spotted crossing the Canadian border, police said.

The 16, 17, and 18-year-old teens, who are from the country of Burundi in eastern Africa, went missing Tuesday after participating in the FIRST Global Challenge robotics competition, NBC Washington reports.

D.C. Metropolitan Police Department spokeswoman Aquita Brown said police had obtained reports that Audrey Mwamikazi, 17, and Don Ingabire, 16, crossed the border into Canada.

Police say they do not suspect foul play was involved in the teens’ disappearance.

“We don’t have an update on the whereabouts (of the others), but we have no indication that there was foul play,” police spokeswoman Margarita Mikhaylova told USA Today.

The missing teens include four males and two females.

MPD identified them as Don Ingabire, 16; Kevin Sabumukiza, 17; Nice Munezero, 17; Audrey Mwamikazi, 17; Aristide Irambona, 18; and Richard Irakoze, 18.

The FIRST Global robotics competition hosts teenagers from nearly 160 nations, according to the competition’s website. The competition drew international media attention when President Trump intervened to allow a team of girls from Afghanistan to enter the country after they had been rejected for U.S. visas twice.

Joe Sestak, a former Democrat congressman and president of FIRST Global, placed a call to police after competition organizers notified him that the team’s mentor could not locate the students following the competition, according to a statement released by the organization.

“Security of the students is of paramount importance to FIRST Global,” the statement says. “FIRST Global ensures that all students get to their dormitories after the daily competition by providing safe transportation to the students staying at Trinity Washington University who are always to be under close supervision of their adult mentor and are advised not to leave the premises unaccompanied by the mentor.”

The mentor told police that all the teens had one-year visas to remain in the U.S.

The Embassy of Burundi in D.C. claimed Thursday morning that the embassy had no idea that the students were in the U.S. until they went missing and added they are not obligated to track their whereabouts while in the U.S.

This is the first time a youth robotics team from Burundi has competed in an international competition, the team’s coach told Chinese news outlet Xinhua News Agency.

Police say the investigation is ongoing.