A man was found dead in a public pool on the city’s Southwest Side early Monday.

Police officers pulled the body of a 27-year-old man out of the Chicago Park District’s Franklin Park pool Avenue around 12:50 a.m. after he was found unresponsive in the water.

Upon arrival, emergency responders and paramedics spent several minutes trying to revive the man and performing CPR before pronouncing him dead.

Fire officials said the cause of death is believed to be accidental drowning.

The pool in the 1400 block of South Kolin Avenue is surrounded by a tall iron fence and closes to the public at 7 p.m. daily, police said, so how the man got inside after hours is still in question.

According to the Centers for Disease Control and Prevention, there have been 3,500 fatal unintentional drownings annually for the past decade, or an average of roughly 10 per day. The CDC reports roughly 80 percent of the drowning victims are male.

Monday marked one of the hottest days of the week in Chicago and the first day of summer.

The drowning has park district officials warning swimmers about safety.

"You always want to swim when there's a lifeguard," said Eric Fischer with the Chicago Park District. "So when there's no lifeguard present, there's no swimming."

The park district and the West Cook YMCA in Maywood are also offering free swim lessons.

The free lessons begin July 5 at the Maywood public pool managed by the West Cook YMCA.

"We feel it's very important to provide free swim lessons here in the community," said West Cook YMCA CEO Phillip Jimenez.