ATLANTA, Georgia (CNN) -- A teenager Saturday was struck and killed by a roller coaster at the Six Flags Over Georgia theme park outside Atlanta, authorities said.

The 17-year-old park visitor was killed after scaling two fences -- one of which was six feet tall -- around the Batman roller coaster, park spokeswoman Hela Sheth said in a statement.

The teen, who visiting the park with a church group from Springfield, South Carolina, was decapitated, she said.

It was unclear how fast the outside-looping coaster was moving when it struck the teen, but according to the park's Web site, the ride reaches speeds of 50 mph.

"We do not know why this person was intent on gaining access to this restricted area," the statement said, noting that multiple signs are posted stating, "Danger Zone," "Do Not Enter" and "Authorized Personnel Only." Watch a park patron describe the scene »

"Some witnesses have stated that the individual was trying to retrieve something he had lost," Sheth said. "Others reported that he was trying to touch the ride. This is merely speculation at this point, and we are working with park visitors and local police to learn more."

No one on the ride was injured, she said.

Police said the incident occurred about 2 p.m. The ride was closed Saturday, but park officials said they expected it to reopen Monday.

The victim's family was at the park with him, Sheth said, and park representatives were with them Saturday evening.

"Our thoughts and prayers are with the family," she said.

Cobb County police spokesman Dana Pierce said officers would continue to investigate the incident, but "all indications are that the park had done everything they could to maintain a safe environment." Watch how day at amusement park turns into a tragedy »

In May 2002, a worker was killed after he walked under the Batman roller coaster's track and was struck in the head by a passenger's leg, according to The Associated Press. After the incident, the ride was inspected and deemed safe by the federal Occupational Safety and Health Administration, AP reported.

In June, a girl's feet were cut off when a free-fall thrill ride malfunctioned at the Six Flags Kentucky Kingdom Amusement Park in Louisville, Kentucky.

A cord wrapped around the 16-year-old's feet and severed them at her ankles while she was on the Superman Tower of Power, a police dispatcher said.

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