The NYPD and the Bureau of Alcohol, Tobacco, Firearms and Explosives are asking the public’s help with the investigation into an explosion in Central Park that took a college student's leg.

Officials are offering up to $40,000 in reward money for information that leads to an arrest and conviction in the July 3, 2016 incident.

It happened on a rock formation near 60th Street and Fifth Avenue.

Connor Golden, who was 18 years old at the time, lost his lower leg when he jumped down from the formation, apparently triggering the explosion.

In addition to tips, investigators are seeking photos and video taken near that location in the hours and days before the explosion occurred.

"The NYPD continues to use every investigative tool to find who may have placed this explosive material in Central Park," said NYPD Commissioner James P. O’Neill. "Someone, somewhere, knows something about this explosion that left a young man severely injured. We want to talk to them. No detail is too small."

"We want our parks and public spaces to be safe for everyone and we want justice for the victim," said ATF Special Agent in Charge Ashan M. Benedict. "Any person who may have any other information regarding the explosion is strongly encouraged to contact ATF or the NYPD."

Police have not had any solid leads since the incident.

"Right now, we're still missing a lot of answers," NYPD Chief of Detectives Robert Boyce said at a press conference Wednesday "We think it was there over several days. It was placed there; we don't know why at this point."

Police said terrorists have used the compound before, but they do not believe the blast was an act of terrorism.

"There wasn't a timer, shrapnel, and other things, and it was left 50 feet from the main road on one of the most crowded weekends in Central Park," John Miller, NYPD's deputy commissioner of intelligence and counterterrorism.

Police said that although the materials used in the bomb are easy to obtain, they believe the suspect or suspects must have a background in chemistry.

"These components you can look up online, unfortunately, and get an understanding of it, but not actually mixing them together," Boyce said.

Police say photos or videos near the rock, days or even weeks before the bombing, could help them.

Anyone with information on the case should contact the Crime Stoppers hotline at 1-800-577-TIPS, or text CRIMES and then enter TIP577, or visit www.nypdcrimestoppers.com.