"The investigation into illegal state border crossing and violation of international flight rules has been launched," the Office said in a statement.
The investigation, launched by the State Border Guard Service, will be centered on a flight on 4 July when representatives of a Swedish PR company flew into the territory of Belarus from Lithuania and airdropped hundreds of teddy-bears with attached messages promoting the freedom of speech and human rights.
Asked by BNS why the investigation was launched more than a month after the incident, the Prosecutor General's Office said the move followed receipt of necessary documents from responsible institutions.
"The pre-trial investigation into alleged violation of the border of the Republic of Lithuania was launched after the State Border Guard Service received necessary information about the 4 July flight. Lithuania's Civil Aviation Administration handed over the information to the State Security Department and the department handed it over to the Prosecutor General's Office. It was then handed over to the State Border Guard Service," the Prosecutor General's Office told BNS in a statement presented by spokeswoman Rūta Dirsienė.
The Belorussian authorities initially denied that such a flight took place. But after less than a month, President Alexander Lukashenko sacked the commander of the country's Air Force and ordered the Swedish ambassador out of the country. Belarus also officially sent a legal assistance request to the Lithuanian Prosecutor General's Office asking for help in investigating the incident.
Prosecutors on Thursday refused to comment on how Lithuania plans to respond to the Belorussian request.
"The Prosecutor General's Office will not comment on the issue as legal assistance requests are meant for mutual communication and help between proper state institutions," Dirsienė told BNS.
Asked last week whether the State Border Guard Service was planning any actions regarding the incident, spokesman Rokas Pukinskas told BNS the Air Force is in charge of protecting the country's airspace.
"I can tell you that the Air Force is responsible for airspace control. We have neither technical means nor the function of airspace monitoring. Talk to the Air Force," he said.
"We don't have any equipment to monitor, say, objects flying in the air, to identify their itineraries, identify their coordinates, direction, etc. You are not the first person to ask me that and in this case we have nothing to say," Pukinskas added.
Following the expulsion of Swedish diplomats from Minsk, Belorussian Ambassador to Lithuania, Vladimir Drazhin, was summoned to the Lithuanian Ministry of Foreign Affairs on Tuesday where he was informed about the European Union’s dissatisfaction.
"It was underlined during the meeting that the Belorussian government's decision on the expulsion of Swedish diplomats will affect not only bilateral relations between Sweden and Belarus but will also have an impact on relations between the EU and Belarus," the foreign ministry said in a statement.
The whole situation will be discussed by the Seimas Committee on National Security and Defense on 21-22 August.
Opposition parties earlier criticized the response of state institutions to the incident. On Thursday, Deputy Speaker of the Seimas and leader of the ruling Liberal and Center Union, Algis Čaplikas, criticized state leaders for their "indifferent position." He believes the Lithuanian Air Force should take responsibility for failure to spot and prevent border violation incident.
"The Swedish PR company organized the teddy-bear stunt and successfully menaced to Lukashenko. And our military and politicians are just shrugging. It’s not an adequate reaction. Let's talk about what Lithuania got from this story. It just got potentially damaged foreign policy and business relations with Belarus," Čaplikas said.