The gate of the Cleveland Dam has been locked in place as officials investigate what caused it to release a violent torrent of water onto the Capilano River Thursday, killing at least one person.

But officials with the Metro Vancouver Regional District stressed Friday that the dam is safe, and its structural integrity remains intact.

"I want to be clear that there was no failure or problem or breach with the dam itself," said commissioner Jerry Dobrovolny at a news conference. "What happened yesterday was with the gate."

The gate controls the flow of water into the Capilano River, and was somehow lowered early Thursday afternoon during regular maintenance, unleashing what witnesses described as a wall of water that swept away several people who were fishing nearby.

Two of the victims managed to make it to shore by themselves, while two others had to be rescued. One man died, and another person believed to have been in the area at the time has since been reported missing.

Despite reports, the dam has no alarm system, he said, and the only warning for people using the river below is a series of signs.

“There’s no publicly facing alarm on the dam. No sirens, no flashing lights, anything like that,” Dobrovolny said.

That was the same situation more than 20 years ago, when Squamish councillor Wilson Williams recalls getting swept away by a similar surprise surge.

“I ran for shore, ran for dear life, got swept out about 12 feet and was able to grab onto a rock and pull myself to shore,” he said.

“It was a traumatizing experience,” he said, adding that the Squamish Nation, whose land is downstream from the dam, is among those looking for answers.

Metro Vancouver chair Sav Dhaliwal told CTV News the incident is a “great tragedy.”

“We very seriously are going to follow through that this does not occur again,” he said. “We don’t know what led to it, but it’s something that we will find out in due course.”

Dobrovolny said regional officials will be investigating throughout the weekend, looking at everything from computer systems and operating protocols to "mechanical and human error."

"My experience, from over 33 years working with infrastructure, is that when a major failure like this occurs, it generally is a combination of both human error and system error," he said.

"We're interviewing staff, we're collecting data, we're checking all of the systems involved. We're doing a very thorough investigation and we will get exactly to the bottom of this and be able to explain what happened."

An emergency operations centre has been set up while the probe continues.

Dobrovolny said the water supply in Capilano Lake, the man-made water body held back by the dam, is abundant enough that the gate can remain locked at its current position throughout the winter, and he expects it will.

"As we get into late spring and start to approach the dry summer season we do need to raise the gate up to its maximum value so we can retain as much water as possible in the lake," he added.

Publicly available readings on the Metro Vancouver website show just how rapidly the river surged on Thursday, shooting up from about 0.6 metres to 4.2 metres before dropping back down again just as quickly.

Officials said the maximum level the river reached wasn't far off from readings that were recorded during September's heavy rain storms. What set it apart was the rapidness of the sudden and unannounced surge.

There are signs along the river warning visitors about the possibility of fast-flowing water, Dobrovolny said, but they were never intended to alert people about the kind of deadly accident that took place on Thursday.

"The rapid change that happened yesterday was not what was intended to be covered by that," he said.