The Victoria Police anti-bikie Echo Taskforce is overseeing an investigation into an incident on Saturday in which two men allegedly bearing weapons, including the son of Hells Angels boss Peter Hewat, threatened to bash Andrew Zaf over a disputed debt.

The allegations are corroborated by two witness statements and audio and video recordings, including a short video showing a Hells Angels-owned tow truck removing a car that was blocking the bikie associates from entering a building site.

The revelations highlight the impunity with which organised crime figures continue to operate in the building industry.

They also raise fresh questions about why the state government has not acted on repeated police requests to introduce laws to licence debt collectors, tow truck drivers and building industry "mediators" with crime links.

The revelations have no connection to the building union or Mr Zaf’s claims to the royal commission last week about alleged corruption involving its officials. However, Mr Zaf’s commission witness statement also detailed the involvement of crime figures in the industry and he has separately made allegations in the media about the role of bikies in the sector.

The fresh evidence of bikie involvement comes after the royal commission heard allegations on Tuesday about the ties between the NSW branch of the CFMEU and suspected Sydney crime figure George Alex, who has close ties to the Comanchero outlaw motorcycle gang.

Former veteran CFMEU official turned whistleblower Brian Fitzpatrick said in sworn evidence that he received a death threat from fellow union official Darren Greenfield after questioning the union’s support of Mr Alex’s crooked building companies and their repeated failure to pay union members superannuation and other benefits.

A recording of Mr Fitzpatrick reporting the threat to police soon after it occurred was also played to the commission.

The incident in Melbourne on Saturday involving Mr Zaf occurred at an excavation site in Melbourne’s outer north.

Echo Taskforce Inspector Ian Campbell said his detectives were overseeing an investigation into the incident.

“The Hewats and the Hells Angels are one of the major focuses of police and we are monitoring this situation closely,” he said.

Fairfax Media has obtained video footage that shows an 888 tow truck, which is owned by Peter Hewat, parked at the front of the site where Mr Zaf was performing earth works with a second man.

Last year, in a widely reported raid, police searched the premises of 888 Towing and allegedly uncovered ecstasy, a taser stun gun, boxes of bullets, a stolen excavator and a rebirthed truck.

Mr Zaf and a witness have told Victoria Police that two men, including Mr Hewat's son, Beau Hewat, threatened Mr Zaf while holding bars after Mr Zaf refused to allow them to remove a machine from the site.

Beau Hewat is a close associate of the Hells Angels and has been previously recorded on phone taps operating the 888 business on the orders of his father.

The machine Mr Hewat was seeking to remove is owned by Melbourne building company Maxstra and was being held by Mr Zaf as security for a debt he claimed was owed to him by Maxstra. Maxstra had organised for 888 Towing to attend Mr Zaf’s site after he had earlier demanded the firm pay his debt.

Mr Zaf and a witness have alleged to police that after Mr Zaf parked his car in front of the entrance to the site and called triple-0, Mr Hewat and his associate used the tow truck to pull Mr Zaf’s car away from the site entrance.

Mr Zaf’s police statement says that after he locked himself inside an excavator, Beau Hewat approached him with “a steel tyre lever in his left hand''.

''The passenger [of the tow truck] had a polished wood bat in his right hand.” The pair allegedly threatened Mr Zaf.

“I panicked and called 000 again,” Mr Zaf said.

A witness is heard on a video recording made immediately after the incident that "Hells Angels" had made threats "with a baseball bat”.

On Tuesday this week, three days after police launched an investigation into the Saturday incident, Maxstra moved to repay the debt to Mr Zaf. Mr Zaf has informed police about this offer.

A Maxstra senior employee, Frank Nadinic, told Fairfax Media that while he was aware the company had ordered a tow truck to Mr Zaf’s building site, he was unaware of the involvement of bikies.

Fairfax Media has previously reported that two serving Victorian building union officials are linked to the rebels outlaw bikie club and that, in 2005, the then fiancee of Victorian union boss John Setka briefly owned a construction business with Queensland Hells Angels boss Errol Gildea.