The alleged 'middleman', in the Daphne Caruana Galizia murder plot, is still being questioned and has not yet been granted a presidential pardon offered in exchange for information, Prime Minister Joseph Muscat has said.

Dr Muscat also revealed businessman Yorgen Fenech’s arrest on Wednesday was not a result of details supplied to the investigators by the so-called 'middleman', Melvin Theuma.

Under Maltese law, detectives have until Friday to charge or release Mr Fenech, but Dr Muscat said officers were considering seeking an extension to the 48-hour deadline that a suspect can be held under arrest. 

Video: Mark Zammit Cordina

Asked about whether Mr Theuma, who was arrested a week ago on unrelated charges, had accepted his conditional offer on immunity, Dr Muscat said questioning was still ongoing. 

“This is one of the reasons why I'm not answering all the questions because right now the person who has offered to give information has not given the full information yet,” Dr Muscat said.

He insisted this is “a sensitive time” and so he did not want to speculate.

On whether Mr Fenech will be charged in court on Thursday, in light of the fact that he had to arraigned within 48 hours of his arrest, Dr Muscat said the police were working on the case to ensure it was closed as soon as possible.

"Now I hope that this case is closed within the next 24 hours. It might be closed within the next 48 hours it might be closed within the next couple of days. Once the case is closed, I will make the necessary considerations."

He pointed out, however, that there were also ways to extend this time-window. He did not divulge any information on whether this was what the investigators were planning to do.

The Prime Minister was answering questions from journalists outside a public cleansing conference he was attending at the Excelsior hotel in Floriana.

Asked whether he would clean out his cabinet, after concerns about the connections between his chief of staff Keith Schembri, Tourism Minister Konrad Mizzi and Yorgen Fenech, he said he would let justice take its course.

"I think what we're doing right now is that we're making sure that the country is clean from criminals, and that we're making sure that there is no impunity," he said.

He said he was being cautious about his words because he didn't want to undermine the investigation.

"Hopefully in the next few days I will be in a better position to answer in a deeper manner, all the questions that you have, but I think that, you know where we're heading right now and you know that the institutions are doing their job," he said.

On whether his chief of staff had turned up at work on Thursday, Dr Muscat said he did not know. 

“I haven't turned up to work yet so I don't know if Mr Schembri is at the office this morning. I'm just coming from Gozo and I have a personal appointment right now so I don't know,” he told Times of Malta.

Mr Schembri has publicly acknowledged having what he described as "draft business plans" with 17 Black, a Dubai company owned by Mr Fenech.