An explosion in August that year ripped through an underpass popular with shoppers using kiosks and commuters walking to the subway.
"According to our information, the perpetrators of this terrorist attack are in all likelihood no longer alive," Yury Semin said.
He said there was a distinct "Chechen trail" in the crime.
"I know this case very well," he said. "Considering that almost six years have passed since then and the attackers are most likely dead, we will probably put this case on hold."