Safety experts are investigating what led a popular thrill ride at a Vancouver amusement park to malfunction mid-ride Monday afternoon, leading to what witnesses called a “horrible metal cracking sound” as oil spilled on riders and those who looked on in horror.

The pendulum-style ride, dubbed the Beast, was immediately brought to a stop, with all riders evacuated immediately, and the ride shut down indefinitely. No one was injured.

Irene Morrison was watching from the ground as her son and nephew swung and spun back and forth to a height of over 125 feet, at speeds of 90 km/h, when she knew something had gone wrong.

“I knew right away something was wrong, because my son has been on the Beast many times, and it doesn’t sound like that,” Morrison said. "It was absolute terror for my sister and I to watch."

"I was worried that something was going to happen and the entire thing was going to fall apart," said her nephew, 11-year-old Kirin Dyck.

On Tuesday, Playland spokesperson Laura Ballance told CTV News a part failure caused the breakdown, though they’re currently assessing the ride, and they’re not sure which part failed.

“These obviously are big machines,” Ballance said. “Parts break. It can be scary for people. But it was not in any way a structural failure.”

Ballance added in this case the ride operator did exactly what he or she was trained to do, which was to bring the ride to a slow stop.

Technical Safety BC, which regulates amusement park rides in the province, confirmed on Tuesday a safety team would be onsite examining the Beast, and that it had “instructed Playland not to operate the ride until we can inspect it and ensure that any potential issues have been resolved.”

Witnesses and riders, including Irene Morrison and her son and nephew, also described being covered in a shower of oil.

“Their bags are soaking, their arms, their shirts, their pants, everything is soaking,” she said.

Ballance apologized to guests and acknowledged the experience was “scary.” She says all impacted guests were taken care of at the time, and that information was handed out on how to clean the oil, which she said was “non-toxic.”

Playland’s Ballance called ride protocols in BC “exceptionally high” and says rides are inspected by Technical Safety BC, at least once a year by independent outside experts, and undergo a daily inspection before operations.

In July 2017, a similar-style ride called the Fireball suffered a structural failure at the Ohio State Fair, killing a teenager, and injuring seven other riders.

That ride is made by Dutch manufacturer KMG, which also built the Beast, with some key important differences: the version in Ohio was a travelling model that was also significantly older at the time of the accident.

The manufacturer later said that excessive corrosion on a support beam lead to catastrophic failure on Fireball.

At the time, Playland shut down and voluntarily inspected the Beast, which opened new in 2015 and is a permanent-fixed attraction, as a precaution.

Irene Morrison said she didn’t think the ride should be shut down permanently after Monday’s malfunction, but said she wanted concrete answers.

“I kind of want to know what exactly happened. And I want to make sure it doesn’t happen again,” she said.

When asked if he would still ride the Beast, her nephew Kirin Dyck said: “I don’t know…it really scared me.”

And while the safety assessments and repairs will take a “few days” at the very minimum, Ballance wouldn’t speculate as to when the Beast might re-open, or if it would be operation for the Fair at the PNE, which begins this Saturday.

“What I can guarantee you is it won’t run one minute earlier than it should,” Ballance said.  

With files from CTV News Vancouver's Angela Jung and Sheila Scott