The PGA Tour said that two lightning strikes hit East Lake Golf Club at 4:45 p.m. ET, 28 minutes after the third round was suspended due to thunderstorms in the area. The Tour said that a tree in the area between the practice range, the 15th green and the 16th tee "was hit and debris from that strike injured four people."
The Tour added that six fans were taken from the course in ambulances for further medical attention. Atlanta Police spokesman James H. White III said the six had sought shelter beneath the tree that was struck by lightning. He said they were taken to hospitals for further treatment, all of them alert, conscious and breathing.
"Our latest report is that their injuries do not appear to be life-threatening," the statement added.
Brad Uhl of Atlanta was crammed under a hospitality tent to the right of the 16th hole that was open to the public.
"There was just a big explosion and then an aftershock so strong you could feel the wind from it," Uhl told The Associated Press after the last of the ambulances pulled out of the golf course. "It was just a flash out of the corner of the eye. It was raining and everyone was huddled near the tree."
Uhl said the people on the ground were moving around before the ambulances arrived.
Play was officially suspended for the day at around 5:30 p.m. The third round will resume Sunday at 8 a.m. ET with Justin Thomas leading Rory McIlroy and Brooks Koepka by one stroke. Thomas said players were eating in the clubhouse when "it felt like the entire clubhouse shook" from the thunder clap.
"The first I heard anything was from one of my friends who came out to watch," Thomas said. "He said, 'Dude, I think someone got struck by lightning right next to us.' And then word started spreading."
Thomas said he had left tickets for another friend who was on the opposite side of where the tree was hit.
Mark Russell, the PGA Tour's vice president of rules and competitions, said signs were posted on scoreboards of severe weather approaching.
"When we suspend play, we encourage everybody to leave and take shelter anywhere they can," Russell said. "We opened up hospitality areas that are grounded, a lot of other places like that. You've got a lot of people, and you have to do that quickly, and sometimes people don't take shelter."
PGA Tour-sanctioned events have not had a death from lightning since the summer of 1991. One man was killed and five were injured from lightning at the U.S. Open at Hazeltine outside Minneapolis. Two months later, a man was struck and killed by lightning walking to his car during a storm delay at the PGA Championship at Crooked Stick in Indiana.
The Associated Press contributed to this report.