Kansas City, Kan. — Two maintenance workers at a Kansas water park where a 10-year-old boy was decapitated on a water slide were indicted Wednesday on charges of obstruction of justice.

David Hughes, maintenance supervisor at the Schlitterbahn Water Park in Kansas City, and John Zalsman, a maintenance worker, pleaded not guilty during a first appearance in Wyandotte County Court.

Caleb Schwab was killed while riding the 17-story Verrückt water slide on Aug. 7, 2016. The park’s co-owner and the designer of the ride have also been indicted in his death.

The latest indictment involves whether a brake mat meant to slow the rafts on Verrückt was repaired after it allegedly fell off on July 28, 2016, just days before Caleb was killed, The Kansas City Star reported.

Authorities allege that Hughes and Zalsman told agents with the Kansas Bureau of Investigation that the brake mat was never on the ride after Verrückt opened in 2014. However, a rider’s GoPro camera showed the brake mat was in place on June 10, 2016, 18 days before it allegedly fell off, according to the indictment.

A third maintenance worker, who was not charged in Wednesday’s indictment, changed his story about the brake mat after seeing the video. He told agents that Hughes and Tyler Miles, a former director of operations for the water park who is also facing charges, were responsible for telling maintenance crews to make repairs, according to the indictment.

Assistant Kansas attorney general Adam Zentner described the new charges as a “very isolated incident.” He said evidence in their matter involved “substantially reduced evidence” compared to other defendants previously charged in Schwab’s death.

Hughes and Zalsman were released from custody on $10,000 bonds. They and their attorneys did not comment after leaving the courtroom.

Schlitterbahn said officials had no reason to believe any employee obstructed justice.

“John and Dave have decades of experience in maintenance and are respected professionals on our maintenance team,” Schlitterbahn spokeswoman Winter Prosapio said in a statement.

The most serious charges have been filed against Schlitterbahn co-owner Jeff Henry, Verrückt designer John Schooley and general contractor Henry & Sons Construction. Each is charged with second-degree murder, aggravated battery and aggravated endangerment of a child. They have all pleaded not guilty.

Miles is charged with involuntary manslaughter, aggravated battery and endangerment of a child, as well as obstruction of law enforcement. Miles was accused of not providing evidence to law enforcement and covering up evidence of previous rider injuries. Miles also has pleaded not guilty.