NAIROBI, Kenya (AP) -- Kenya's security services made another arrest Sunday in connection with the deadly Westgate mall attack, a top official said, but declined to say how authorities believe the person was involved in the siege.
Kenya has arrested 12 people since the attack but three have been freed, Interior Minister Joseph Ole Lenku said during a press conference. He declined to say if any of those arrested had been in the mall during the attack.
Investigators have also identified a car used by the gunmen, from the Somalia-based Islamist group al-Shabab, and found in it "an assortment of illegal weapons," said Lenku.
The four-day siege, which included the collapse of part of the mall, left 67 people dead, according to officials. The Red Cross says 59 people remain missing, though the government puts that number at zero.
Kenyans have become increasingly frustrated over the government's unwillingness to share information about the attack. Almost no details have been released about what happened after the first hours of the siege.
"We ask you to bear with us," he said, of the government's unwillingness to share information.
While the mall was a chaotic scene for many hours after the attack began, with people moving in and out of the upscale shopping center, Lenku insisted no terrorists could have escaped.
"Our forces sealed off every point of exit," he said. "It was completely secured."
Earlier Sunday, about 200 Kenyan Muslims held a rally near the mall to remember the dead and call for peace.
"We condemn the terror attack on Westgate Mall," said one sign. "One Country. One People. One Love. Kenya Asia Muslims," said another.
Many of those at the rally were from Kenya's "Asian" community, the descendants of people who came from colonial India -- what is now India, Pakistan and Bangladesh -- to work in Kenya more than a century ago.