Ontario's police watchdog has cleared a Niagara regional officer in the death of an 18-year-old man who fell into the Niagara Gorge.

The Special Investigations Unit says Const. Jacob Smits was trying to arrest Ryan Dube, who was wanted for breach of probation, on July 24 when Dube fled.

The SIU says Dube ran down an incline to a retaining wall in front of the gorge, then climbed over the wall as Smits chased him, following him over the wall a few seconds later.

Both men fell more than 20 metres, then slid another 20 metres down a 45-degree rock formation.

Smits radioed for help and members of the police emergency task unit rappelled down the gorge to find both men but Dube — who was severely injured — died before he could be lifted out.

The SIU says Smits, who was rescued with a fractured thigh, had lawful authority to arrest Dube as well as to apprehend him when he fled, and was not responsible for his death.

"Unfortunately, Mr. Dube chose to escape apprehension by jumping over a retaining wall and placing himself in significant jeopardy," said Ian Scott, director of the watchdog agency.

SIU investigators interviewed four witness officers and 17 civilian witnesses during their probe into the incident. Smits did not participate in an interview or provide a copy of his duty notes, as is his legal right.

The SIU is an arm's-length agency that investigates reports involving police where there has been death, serious injury or allegations of sexual assault.