TORONTO -- Two eye witnesses to the deadly Downsview Park stage collapse speculated Sunday that heavy machinery hanging from the structure's ceiling may have caused the killer cave-in.

The man who died in Saturday's the tragic mishap was identified as Radiohead drum technician Scott Johnson, 33, of the United Kingdom.

Stephanie Heintzman and Liz Pashkov, both 22, were working at a Downsview Park beer tent Saturday and finished preparing early. They decided to check out the stage where Radiohead would be performing.

Heintzman, a recent University of Waterloo psychology grad, said lights and screens at the top of the stage appeared to be "way too heavy."

She remembers clearly because she took pictures of the equipment as Pashkov chatted with a group of men working on the stage.

As the girls walked back to the beer tent, Heintzman said they heard a "clicking, tick, tick, tick" sound and turned around to see the stage collapse on the men.

"It looked like a lot of complex equipment being suspended from the ceiling bars," added Pashkov, a recent Ryerson University nursing graduate.

"I stood frozen because I couldn't believe what happened and it hit me that people were underneath."

She said people shouted to find out if anyone was hurt.

"There was no answer and that struck panic in everyone," added Pashkov, who ran towards the stage instinctively to help the injured.

Pashkov found a man trapped, his head gashed open and bleeding. She waited with him until emergency crews arrived.

Matt Blajer, a spokesman for the ministry of labour -- which is looking into the collapse -- said Sunday that three investigators and two engineers were on site.

"I know nothing about that," Blajer said of the heavy ceiling machinery. "But that's probably something we're looking at, too."

Blajer said the inspectors requested and received engineering drawings of the stage.

He added "there are regulations around rigging stages" and the inspectors will determine if they were followed during what will likely be a lengthy investigation.