Police have recovered 500 rounds of ammunition from the set of Rust.
Actor Alec Baldwin accidentally shot and killed cinematographer Halyna Hutchins and wounded director Joel Souza on the set of the Western last week and police have confirmed criminal charges may still be filed.
District Attorney Mary Carmack-Altwies said of potential charges. "All options are on the table. No one has been ruled out at this point."
Investigators in New Mexico said a "lead projectile" had been removed from the director's shoulder and it appeared to be a live round. It has been submitted as evidence, along with an additional 600 items, including three firearms and 500 rounds of ammunition.
Presenting their initial findings, Sante Fe County Sheriff Adam Mendoza added: "We suspect there were other live rounds found on set.
"We're going to determine how those got there, why they were there, because they shouldn't have been there."
He also warned there had been "some complacency" around safety on the set, telling reporters up to 100 people had been there when the shooting happened, including armourer Hannah Gutierrez-Reed and assistant director Dave Halls – both of whom had handled the antique Cold .45 revolver before it was given to Baldwin.
He said: "I think the facts are clear – a weapon was handed to Mr Baldwin. The weapon (was) functional and fired a live round killing Ms Hutchins and injuring Mr Souza.
"We're going to try to determine exactly how (this) happened and if they should have known that there was a live round in that firearm."
A court document made public on Wednesday showed Halls admitted to investigators he had failed to check all rounds in the gun before handing it over to the movie's star, despite reports he had called out "cold gun", confirming he believed it to be safe.
The armourer told investigators that guns had been safely secured shortly before the shooting but ammunition hadn't been. They also confirmed the weapons were usually kept in a safe, which only a few people had access to.
The sheriff thinks Hollywood needs to address safety protocols, adding: "Obviously I think the industry has had a record recently of being safe. (But) I think there are some safety issues that need to be addressed by the industry and possibly by the state of New Mexico."
Baldwin and the producers have reportedly hired a private law firm to conduct an investigation into the shooting.