"There's a determination to find out if these letters are authentic and this will be done in the Seimas," Ramūnas Karbauskis, the ruling party's leader, told reporters on Thursday.
"We understand that these letters are at the prosecutor's office and that these letters should be in the Seimas servers. One of the media companies has them. The first two sources should confirm if they are authentic," he added.
According to Karbauskis, if previously unknown circumstances emerge, the parliament might ask for access not only to Masiulis' emails, but also to those by other politicians in order to get a full picture.
The Seimas Committee on Legal Affairs will look at how many and what emails between politicians could be retrieved from the parliament's servers, he added.
Agnė Širinskienė, the committee's chairwoman, said on Wednesday that the circumstances surrounding the prosecutor general's appointment, as allegedly discussed in Grybauskaitė's emails with Masiulis, could be the subject of a parliamentary investigation.
Grybauskaite said earlier in the day that she had had email exchanges with the former Liberal Movement leader, but added that she could not confirm the authenticity of the letters published in the media.