Kenya mall attack suspect eyed after ammunition fell out of his pocket

NAIROBI, Kenya (CNN) -- A man who cast himself as a victim of the recent attack on a Nairobi mall gave himself away as a possible suspect when a machine-gun magazine fell out of his pocket as he was being evacuated, a Kenyan counterterrorism source said Thursday.

This Kenyan national, who was injured in the ordeal, is currently being held in a hospital at a military airbase, according to the source.

It was not immediately clear if this man is one of the at least 10 individuals who Kenyan officials have said are in custody on suspicion of taking part in the Westgate Mall attack.

There is increasing concern that some perpetrators escaped the mall along with fleeing civilians, and thus remain at large, U.S. law enforcement officials say. U.S. forensic investigators were granted access to the ravaged mall on Thursday.

The onslaught began when militants stormed the upscale Nairobi shopping mall on Saturday, forcing shoppers and diners to run for their lives or scramble for safe hiding spots. It ended on Tuesday, by which time President Uhuru Kenyatta said authorities had overrun the gunmen and taken over the mall.

Al-Shabaab, a Somalia-based terrorist group with links to al Qaeda, took credit for the carnage.

In addition to five terrorists, at least 67 people are confirmed dead in the attack. Officials fear that number could rise -- as many as 63 people are still unaccounted for -- as they sift through the rubble left from the collapse of three floors of the expansive facility.