KUALA LUMPUR, Malaysia — Police arrested a second woman Thursday in the death of Kim Jong Nam, the half brother of North Korea’s leader who was reportedly poisoned this week by two female assassins as he waited for a flight in Malaysia.

Police chief Khalid Abu ­Bakar confirmed the latest arrest to the national Bernama news agency and said a statement would be released soon.

Investigators are trying to shed light on a death that set off waves of speculation on whether North Korea dispatched a hit squad to kill a man known for his drinking, gambling, and complicated family life.

Medical workers completed an autopsy late Wednesday, but it was not immediately clear whether or when Malaysia would release the findings publicly.

North Korea had objected to the autopsy and asked for Kim Jong Nam’s body to be returned; Malaysia went ahead with the procedure anyway as the North did not submit a formal protest, said Abdul Samah Mat, a senior Malaysian police official.

Also Wednesday, police arrested the first suspect in the case, a woman carrying Vietnamese travel documents bearing the name Doan Thi Huong. She was picked up at the budget terminal of Kuala Lumpur International Airport, where Kim Jong Nam fell ill Monday morning. It was not immediately clear whether the passport was genuine.

She was identified using earlier surveillance video from the airport, police said.

Still photos of the video, confirmed as authentic by police, showed a woman in a skirt and long-sleeved white T-shirt with ‘‘LOL’’ emblazoned across the front.

Kim Jong Nam, who was 45 or 46, was estranged from his younger brother, North Korean leader Kim Jong Un, and had been living abroad for years. He reportedly fell out of favor when he was caught trying to enter Japan on a false passport in 2001, saying he wanted to visit Tokyo Disneyland.

According to two senior Malaysian government officials, who spoke on condition of anonymity because the case involves sensitive diplomacy, the elder Kim died en route to a hospital Monday after suddenly falling ill at the airport’s budget terminal.

He told medical workers before he died that he had been attacked with a chemical spray at the airport, the Malaysian officials said. Multiple South Korean media reports, citing unidentified sources, said two women believed to be North Korean agents killed him with some kind of poison before fleeing in a taxi.

Police said they were hunting for more suspects. No further details were released.

Since taking power in late 2011, Kim Jong Un has executed or purged a number of high-level government officials in what the South Korean government has described as a ‘‘reign of terror.’’

South Korea’s spy agency, the National Intelligence Service, said Wednesday that North Korea had been trying for five years to kill Kim Jong Nam. The NIS did not definitively say that North Korea was behind the killing, just that it was presumed to be a North Korean operation, according to lawmakers who briefed reporters about the closed-door meeting with the spy officials.

The NIS also cited a ‘‘genuine’’ attempt by North Korea to kill Kim Jong Nam in 2012, the lawmakers said. The NIS told them that Kim Jong Nam sent a letter to Kim Jong Un in April 2012, after the assassination attempt, begging for the lives of himself and his family.

The letter said: ‘‘I hope you cancel the order for the punishment of me and my family. We have nowhere to go, nowhere to hide, and we know that the only way to escape is committing suicide.’’

Although Kim Jong Nam had been originally tipped by some outsiders as a possible successor to his late dictator father, Kim Jong Il, others thought that was unlikely because he lived outside the country, including recently in Macau.

He also frequented casinos, five-star hotels, and traveled around Asia, with little say in North Korean affairs.

But his attempt to visit Tokyo Disneyland reportedly soured North Korea’s leadership on his potential as a successor. Kim Jong Nam had said he had no political ambitions, although he was publicly critical of the North Korean regime and his half brother’s legitimacy in the past. In 2010, he was quoted in Japanese media as saying he opposed dynastic succession in North Korea.