MONROVIA, Liberia (AP) — A speeding vehicle rammed into jubilant supporters of President-elect Joseph Boakai at a victory celebration, killing at least two people and injuring at least 18 others, authorities said Tuesday.

Police made an arrest following the crash late Monday but are withholding the name of the suspect pending their investigation, said Col. Melvin Sackor, deputy police inspector general for operations.

It was not immediately known whether the crash at the headquarters of the Unity Party in Monrovia was politically motivated. However, it took place hours after election officials formally declared Boakai the winner of this month's presidential runoff vote.

According to the National Elections Commission, Boakai won with 50.64% of the second round balloting while incumbent President George Weah took 49.36%.

Weah had already conceded defeat several days earlier based on the release of provisional results, and urged his supporters to respect the vote's outcome.