Just under one year ago, an explosion in Central Park cost Virginia teenager Connor Golden his left leg below the knee, after he stepped on what police have said was a homemade firework. Investigators have never been able to find whoever left the explosive materials on the ground, and are now offering a large reward for any information that could lead to an arrest and conviction in the case.

The NYPD announced today that they're offering up to $40,000 for any tips, pictures or video that helps lead to an arrest and conviction in the July 3rd, 2016 explosion in Central Park near 60th Street and 5th Avenue.

"The NYPD continues to use every investigative tool to find who may have placed this explosive material in Central Park," NYPD Commissioner James P. O’Neill said in a statement. "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."

Last year, police suggested that the explosion was caused by someone who was testing out a homemade explosive because of the presence of TATP (triacetone triperoxide), an explosive substance that attempted shoe bomber Richard Reid attempted to use in 2001. Police believe that after the explosive didn't to off, whoever made it left it in a shopping bag near a rock formation in Central Park, where Golden stepped on it.

The investigation has proven frustrating for the NYPD and ATF, and the reward offered for information on a legitimate suspect has been upped from $10,000 to $25,000 to now $40,000. Lt. Michael Ruzzi, commanding officer of the NYPD's Arson Explosion Squad, told the Daily News that investigating an incident that took place in such a huge, heavily trafficked park "really is a needle in a haystack. But we’re going to look at every piece of hay."