LOS ANGELES, California (AFP) - Lawyers representing the woman who loaded Alec Baldwin's gun said an act of "sabotage" by disgruntled crew members may have caused the tragic shooting on the set of "Rust."

Hannah Gutierrez-Reed was the armorer in charge of weapons on the Western movie set in New Mexico, where Baldwin fatally shot a cinematographer last month after being told his firearm was safe.

Her lawyers told the "Today" program, on the US network NBC, that Gutierrez-Reed had loaded the gun with ammunition from a box of dummy, or inert, rounds and had "no idea" where the live round that killed Halyna Hutchins came from.

"We're assuming somebody put the live round in that box -- which if you think about that, the person who put the live round in the box of dummy rounds had to have the purpose of sabotaging this set," said Jason Bowles.

"There's no other reason you would do that. That you would mix that live round in with the dummy rounds."

Prosecutors have refused to rule out criminal charges over Hutchins' death.

Santa Fe County Sheriff Adan Mendoza has said it appeared "there was some complacency on this set."

There have been multiple reports that "Rust" camera crew resigned the day before the shooting, in part due to significant safety concerns surrounding firearms and explosives on set.

Both Baldwin and Gutierrez-Reed are cooperating with the ongoing investigation.

Pressed on why somebody would deliberately sabotage the production by disguising a lethal round as safe ammunition, Bowles pointed to "unhappy" crew members who had walked out hours before the shooting.

"We have people who had left the set, who had walked out because they were disgruntled," said Bowles, pointing to on-set complaints over long working hours and hotel accommodation for crew.

"We have a timeframe between 11:00 and 1:00 approximately that day in which the firearms at times were unattended. So there was opportunity to tamper with a scene."

Asked why Gutierrez-Reed had left the firearms unattended, Bowles said she had been asked by producers to shoulder additional duties as a "key props assistant," and was attending to those at the time of the shooting.