Several fans of the Kansas City Chiefs who attended a playoff game on a bitterly cold January day in Missouri suffered frostbite that required amputations, according to the hospital that treated them.

Twelve people — including some football fans who were at Arrowhead Stadium on Jan. 13 — had to undergo amputations involving mostly fingers and toes, the hospital, Research Medical Center in Kansas City, said in a statement on Saturday.

The center said it treated dozens of patients who experienced frostbite during an 11-day cold snap. Not all of the patients who had amputations attended the Chiefs game. Some were people who worked outdoors in the extreme cold, the hospital said.

The exact number of fans who attended the game who had amputations was unclear. The hospital said there was some overlap among the fans and those who had also worked outdoors.

The hospital also noted that symptoms of frostbite can develop slowly, and that many of the frostbite patients it treated could not identify when their injuries occurred — when their pain, numbness and other symptoms began.

The hospital said it was a record number of frostbite patients since the burn center opened 11 years ago.