Cape May, N.J. — An off-duty Philadelphia firefighter has died at a Cape May triathlon, fire officials confirm to CBS Philadelphia. The firefighter was competing Sunday morning in the Escape the Cape Triathlon.

It is unclear how the off-duty firefighter died at this time.

The triathlon consists of a 1-mile swim, a 23-mile bike ride and a 5-mile run. Swimmers began jumping off the Cape May-Lewes Ferry around 8:30 a.m. Sunday for the first leg.

Another Philadelphia firefighter also died Sunday morning from long-term medical issues.

Philadelphia Fire Commissioner Adam Thiel announced the news in a tweet.

The identities of the firefighters have not been released at this time.