Earlier this month, the Portuguese Football Federation (FPF) opened an inquiry after an initial report said Queiroz had insulted anti-doping doctors during their surprise visit to the World Cup training camp in May.
"The disciplinary committee wants to hear the national coach on the matter, which has not been possible until now as he is overseas," the FPF said in a statement after a board meeting.
"The intention is to complete the process by mid-August. Due to the urgent nature of the matter, the committee has already met with five witnesses," it added.
According to local media reports, the episode could cost Queiroz his job following Portugal's disappointing second-round exit to eventual winners Spain in South Africa.
Former Real Madrid coach Queiroz has two years of his contract to run with the national team.
In comments broadcast by RTP TV channel earlier on Friday, Queiroz said the inquiry had been handled incorrectly, adding he had "been the victim of a public lynching ... on matters about which I have not even been heard".
Queiroz did not directly refer to the possibility of being fired but said he would lodge a complaint with world football's governing body FIFA if there were irregularities in the probe.
The coach added he was confident that he still had the backing of FPF president Gilberto Madail because he acted only to safeguard the team's interest.
