BUENOS AIRES, Argentina -- The Copa Libertadores round-of-16 match between bitter Argentine rivals Boca Juniors and River Plate was suspended Thursday after River Plate players were sprayed with a substance that seemed to affect their vision and irritated their eyes.

"My whole body hurts," River player Leonardo Ponzio said. "They threw, I'm not sure what it was, pepper spray at us. This just can't be."

The first half of the match ended 0-0. River players rubbed their eyes as they entered the field to start the second half through a makeshift tunnel, many using their shirts to try to clear their vision.

Police and officials of both teams milled on the field for more than an hour before the match was suspended at Boca's La Bombonera stadium.

It was not immediately clear when the game would be completed.

River Plate won the first leg of the two-leg series 1-0 last week.

"It's sad," River coach Marcelo Gallardo repeated several times. "It's unbelievable what happened."

Leonardo Ponzio grimaces in pain after he was apparently sprayed with an irritant during the Boca Juniors-River Plate match Thursday. Amilcar Orfali/Getty Images

Television images showed a fan sliding a hand through the flexible tunnel that shields players entering the field. The images suggested he was spraying some kind of irritant.

About half of the crowd of 50,000 left quickly after the match. Hard-core fans stayed around with players from both teams standing at the middle of the field among police and officials.

This was the third match in 12 days for the two Buenos Aires rivals. Boca defeated River 2-0 to take the lead in the Argentine first division, just ahead of River. Four days later, River defeated Boca 1-0 in the first leg of the round of 16 at River's Monumental stadium.

Violence or threats of violence are endemic in almost every match at all levels in Argentine football. The Argentine Football Association has been criticized for doing little to stem the violence. AFA says it's a societal problem.