In a bid to solve the mystery behind the assassination of North Korean leader, Kim Jong Un’s half-brother, Kim Jong Nam, Malaysian police early Thursday arrested a woman with an Indonesian passport who is suspected to be the second of two women who allegedly carried out the assassination.

Search is still ongoing in a bid to arrest other conspirators.

The suspect, identified as Siti Aishah, 25, is the second woman arrested in the case. Her appearance matches the image of a woman captured in airport surveillance videos, said the statement from Khalid Abu Bakar, the Inspector General of Police.

The first woman who was arrested a day earlier was carrying a Vietnamese passport. The police were trying to confirm whether either passport reflected the women’s true nationalities.

North Korea has long been suspected of training its spies to pose as foreigners. In 1987, when a female officer from the North was caught on suspicion of planting a bomb on a Korean Air passenger jet, she was using a Japanese alias and spoke Japanese.

The news media in Malaysia reported that the police were also looking for four male suspects, suggesting that the plot was more involved than initially indicated.

Channel NewsAsia reported that the police had arrested the woman’s Malaysian boyfriend in the case. It was unclear what role he may have had.

The attack on Jong-Nam, 45, occurred near the AirAsia counter while he was preparing to fly to his home in Macau from Kuala Lumpur on Monday morning.

On his way to the hospital before he died, he told emergency personnel that a chemical weapon was used on him.

Meanwhile, North Korea officials reportedly spent hours on Wednesday trying to talk Malaysia out of conducting an autopsy on Jong-Nam.