The elder brother of Manchester Arena suicide bomber Salman Abedi has left Britain before his appearance at the inquiry hearing into the attack.
Ismail Abedi was due to give evidence at the Manchester Arena Inquiry on Thursday and be questioned over the radicalisation of his brothers Salman and Hashem.
Separately, a childhood friend of the bomber was arrested on Monday trying to leave the country.
Salman Abedi killed 22 people and injured more than 1,000 when he detonated a bomb in his rucksack at the end of an Ariana Grande concert in May 2017.
His younger brother, Hashem Abedi, was convicted last year on 22 counts of murder, one count of attempted murder and one count of conspiracy to cause an explosion.
He was sentenced to jail for a minimum of 55 years.
Although Ismail is not considered a suspect, the interrogation was expected to be uncomfortable for him after the inquiry heard previously that his fingerprints were found on the car used to store the explosives.
Paul Greaney QC, counsel to the inquiry, said on Tuesday that Ismail was not in the country despite being summoned to attend the hearing.
"We understand that he is not currently in the country and there is no indication as to when he may return," he said.
"Ismail Abedi clearly has important evidence to give and we urge him today to make contact with the inquiry legal team, either directly or through his legal team.
"If he does not do so, the public may infer that he has something to hide."
Sir John Saunders, chairman of the Manchester Arena Inquiry, said Ismail Abedi was still summonsed to attend.
The brothers' parents Ramadan Abedi and Samia Tabbal also face scrutiny but are believed to be in Syria.
Mr Greaney said they had been contacted but had refused to help with the inquiry.
Detectives wish to speak to them on suspicion of terrorist offences linked to the forensics and financing of the deadly attack.
A friend of Abedi's, Ahmed Taghdi, was also due to give evidence this week but was apprehended on Monday trying to leave the country.
He is now in custody. The inquiry had issued a legal order to ensure he attended the hearing with a warrant for his arrest if he failed to do so.
Despite the attempt to leave Britain, Mr Saunders said it was the Mr Taghdi's intention to return to the country as he had a return ticket for October 20.
The Manchester Arena Inquiry is examining the circumstances of the attack and whether any opportunities to prevent it were missed.
It is examining the radicalisation of Salman Abedi.