This had indicated that searching for possible accomplices in the raid is gathering pace.
President Uhuru Kenyatta said on Wednesday that a 20-hour siege had ended with security forces killing five militants, who had stormed the hotel complex, forcing hundreds of people into terrifying escapes.
“The detectives are looking for a woman suspected to have ferried weapons from Kiunga through the port city of Mombasa to Nairobi,” a police official said.
Kiunga is a region near the Somali border.
On Wednesday, Inspector-General of Police, Joseph Boinnet, said they had arrested two people in connection with the attacks.
The police official did not say when the other seven were arrested.
Kenya, the East African hub for multinational companies and the UN, became a frequent target for al Shabaab after Kenya sent troops into neighbouring Somalia in 2011 to try to create a buffer zone along its border.
Sixteen Kenyans including a policeman, an American survivor of the Sept. 11, 2001 al Qaeda attacks on the U.S., and a British development worker were among the dead in the hotel 14 Riverside Drive complex attack.
Images of the bloodied bodies of five attackers were broadcast across social media as Kenyatta announced the end of the siege, which echoed a 2013 al Shabaab assault that killed 67 people in the Westgate shopping centre in the same district.
“The investigations into this matter are complex and transnational and would, therefore, require sufficient time and resources to uncover the entire syndicate,” Public Prosecution Director, Noordin Haji, said in a statement.
A team of prosecutors had been assigned to assist the investigators with technical guidance, the statement read.
Investigations will take place in Kenya as well as neighbouring Somalia, where jihadist group al-Shabaab, which claimed responsibility for the bombing and gun attack, is based.