Authorities investigating last month's deadly attack at a Kenyan mall say a Norwegian-Somali man may have been involved.

Norwegian officials have declined to publicly identify the man. However, investigators in Kenya say he is 23-year-old Hassan Abdi Dhuhulow, a Somali-born Norwegian citizen. It is not clear if Dhuhulow is still alive.

Martin Bernsen, spokesman for the Police Security Service in Norway, says authorities there have been investigating the possible involvement of a Norwegian citizen in the mall attack.

In an interview Friday with VOA, Bernsen said the "suspicions had become stronger" within the past week. He said the evidence that has contributed to those suspicions includes mall surveillance camera video and interviews with people who had information about the possible suspect.

Kenyan authorities previously released the names of four other militants they say were involved the attack, all of whom were killed.

Gunmen stormed the Westgate Mall on September 21, setting off a standoff with security forces that lasted for four days. At least 67 people died during the attack and siege, not counting the gunmen.

The Somalia-based al-Shabab militant group claimed responsibility for the attack and threatened to carry out other acts of violence against Kenya.

The rebel group has been demanding that Kenyan forces withdraw from Somalia.

Kenya sent troops to Somalia two years ago to help battle al-Shabab, which has been fighting to turn Somalia into a strict Islamic state.

Investigators continue to gather evidence at the mall, which partially collapsed during the siege.

On Friday, Kenyan officials said investigators had recovered charred remains which may be the bodies of two of the gunmen.