NEWTON (CBS) – A man drowned in a lake in Newton early Wednesday morning.

A group of five people jumped into Crystal Lake just before 2 a.m. when one of them went missing, the fire department told WBZ-TV.

READ MORE: Start Of Bruins Season Brings More Business To Sports Bars Near TD Garden

Crystal Lake in Newton. (WBZ-TV)

Firefighters rushed to the lake and eventually found the man about 20 feet out in the water, unresponsive. He had been missing for 20-to-25 minutes when he was located, authorities said.  He was rushed to Newton-Wellesley Hospital where he died.  Because foul play is not suspected, the Middlesex District Attorney’s Office said it will not reveal his name, only noting that he was 28 years old.

READ MORE: Search For Missing 5-Year-Old Boy Elijah Lewis Continues In New Hampshire

The fire department said the north side of the lake where the man drowned is a popular, but illegal, swimming spot.

“There is no lifeguard on duty in this area of the lake,” the DA’s Office said in a statement.

Swimmers are not allowed in the north side of Crystal Lake in Newton. (WBZ-TV)

MORE NEWS: Boston Police Cruiser, Sedan Collide In Early Morning Crash In Roxbury

The medical examiner will determine the official cause of death.