Police are investigating the sudden disappearance of six teens from the D.C. area after they competed in an international robotics competition this week NBC reports.

The teens, aged 16-18, vanished Tuesday after participating in the FIRST Global Challenge.

The D.C Police Department identified them on Twitter as: Audrey Mwamikazi, 17; Aristide Irambona, 18; Kevin Sabumukiza, 17; Don Ingabire, 16; Nice Munezero, 17; and Richard Irakoze, 18.

Two of the teens, Audrey & Don, were seen crossing into Canada on Thursday, according to Washington police.

No foul play is suspected at this point.

President Joe Sestak of the FIRST Global competition was the first to call the police after the team’s mentor disclosed they could not find the students. A statement from the competition speaks to the safety practices of 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 students, who came to America from Burundi, were granted one year visas to stay in the U.S.