The wave pool at the Mont St. Sauveur Water Park reopened Saturday morning, three days after a nine-year-old boy drowned while on a class trip.

Jeremy Mulumba, a student at l'Aquarelle school in Laval, was pulled from eight feet of water by a lifeguard after he sank in the deep end of the wave pool Wednesday.

It's still not clear why the boy drowned. Officials at the water park say the wave pool can accommodate 700 people, but it was less than half full on the day of the accident – and there are always three life guards on duty.

Parents interviewed by CTV News on Saturday said the incident was alarming.

"Yes, I'm concerned because I thought that the monitors were watching the kids very closely," said Bonavuth Pek.

But others suggested it's up to parents to be more vigilant.

"It's our responsibility to check our kids, so when we come here, we check them, we go along with them, we're sitting near by -- so it's not always the responsibility of the park," said Vicky Elbert.

The Surete du Quebec and a coroner are investigating the drowning.