Members of Kosovo's political opposition released tear gas into a parliamentary session on Wednesday in order to prevent lawmakers from voting on a border agreement they oppose.
Agreement with Montenegro is key condition for visa-free travel to EU's Schengen zone.
The parliament speaker adjourned the session until the room had been ventilated.
"The border demarcation between Kosovo and Montenegro is not a bilateral problem".
Police said they were investigating how the tear gas got into the hall, adding that officers couldn't enter the chamber unless asked by the parliament's leadership. Some experts said the border vote has given the party a chance to reassert its relevance.
The opposition party has used tear gas and similar tactics to disrupt parliament multiple times in the last three years, according to AP. Everyone inside the chamber was forced to leave.
The 120-seat parliament was expected to ratify the 2015 deal, which was set as a precondition by the European Union for Kosovo's citizens to freely travel within its visa-free travel zone known as Schengen.
Two members of the governing coalition were injured on Wednesday, but lawmakers nonetheless pledged that the vote would go forward.
But opposition politicians have alleged that the agreement gives away 8,000 hectares of Kosovo's territory to Montenegro.
European Commissioner Johannes Hahn, who is responsible for relations with the bloc's neighbors, condemned the opposition MPs' actions on Twitter.
Delawie was at the parliament building when the tear gas was released, according to The Associated Press.
"Such behaviour has no place in a democracy".
US Ambassador to Kosovo Greg Delawie also said following the incident that the vote will still take place during the course of the day.
The United States and 23 of the EU's 28 member states now recognize Kosovo as an independent country.