Malaysian Anti-Corruption Commission (MACC) Chief Commissioner Tan Sri Azam Baki has described the alleged corruption involving Immigration officers at the Kuala Lumpur International Airport (KLIA) as a national security issue.
He said the probe was far from over, with a slew of people set to be questioned.
He denied reports quoting an alleged MACC source as saying that the commission did not find any element of corruption in the case, with the source labelling it a "mere misunderstanding".
Azam said the accusations were serious, thus a thorough probe was necessary as it involved the whole department.
"We are gathering evidence and have more statements to record from witnesses in the case. It is irresponsible for anyone to speculate or sensationalise the case while investigations are ongoing," he told the New Sunday Times.
"It has hardly been a week since the investigation into the case was opened. We need time to determine whether there are wrongdoings or elements of corruption as claimed.
"We must investigate those from the Immigration Department, the company appointed to facilitate the Not-to-Land (NTL) visitors and airlines operators to check whether all the standard operating procedures (SOP) were adhered to or breached.
"All this must be carefully detailed before any statement is issued to the media."
Azam said it could not be assumed that the probe was over just because the complainants had returned to their country.
"This is a public interest case involving the country's enforcement and national security."
The issue sparked off when Tourism Art and Culture Minister Datuk Seri Tiong King Sing was accused of "barging into" the KLIA arrival hall on June 30 to intervene in the immigration detention of two Chinese nationals.
Tiong later said he was there in his capacity as a minister to check on claims by foreign travellers of heavy-handedness by Immigration officers.
He claimed that a "culture of corruption" existed among some Immigration personnel at KLIA, and that there were complaints of bribes being demanded from travellers.
Tiong also took issue with the appointment of a company tasked with handling NTL visitors and the alleged lack of transparency involved.
The company, appointed by the Airlines Operators Committee and Immigration Department, had since 2016 handled the expatriation of NTL travelers.
MACC later said it had identified the "middleman" who allegedly demanded an administration fee of RM18,000 to allow one of the tourists to enter Malaysia.
The commission later recorded statements from 14 people, including eight Immigration officers, the two foreigners, Tiong as well as a company director.
The two foreigners were allowed to return to China after their statements were recorded.
An investigation was also launched to examine the role of the company handling NTL passengers.
Attempts have been made to get comments from the Immigration Department, Airlines Operators Committee and the company.