Belgian authorities are looking for a man who was seen together with the chief suspect after the May terror attack at the Jewish Museum in Brussels that left four people dead.

A Belgian judicial official said Friday they were looking to question a bald-headed man with a sporting bag seen walking alongside the suspect four days after the May 24 shooting.

The official, who spoke on condition of anonymity because of the sensitivity of the investigation, said police wanted to question the man as a witness.

The man accused of the killings, Mehdi Nemmouche, was arrested at a Marseille bus station carrying weapons resembling those used in the killings.

Nemmouche is a 29-year-old French national who was extradited to Belgium in July.