Wangaratta police have confirmed their suspicions a fire at the Tone Road Ambulance Victoria headquarters was deliberately lit, with a hoax call made to draw paramedics away from the station.

Detective Senior Constable Aidan Hogan of the Wangaratta Criminal Investigation Unit said police believed accelerant was poured around multiple office spaces at the local ambulance depot between 7:30pm and 9:20pm on Friday 19 June.

Det Sen Const Hogan said once the alleged offender was at the premises, a hoax call was made to have emergency services dispatched to a fake job at North Wangaratta.

About 9:20pm when on-duty paramedics returned, the main office of the Ambulance Victoria depot was on fire.

Wangaratta firefighters attended the incident and brought the fire under control by 9:38pm.

The blaze was contained inside the building, causing serious damage, and no one was injured or onsite at the time.

The Wangaratta office is the headquarters for the Ambulance Victoria Hume region and while Det Sen Const Hogan said Wangaratta paramedics have returned to working at the branch, regional paramedics attached to the Wangaratta headquarters continued to work off-site.

Det Sen Const Hogan said it may take six months to fully complete repairs due to the damage sustained at the station.

An Ambulance Victoria spokesperson confirmed at the time of the incident there would be no service delivery impact.

Det Sen Const Hogan said no arrests had been made yet and the investigation remained ongoing.

Anyone with further information regarding the incident or who may have CCTV or dashcam footage in the Tone Road area at the time is urged to contact Wangaratta police on 03 5723 0888, Crime Stoppers on 1800 333 000 or submit a confidential report online via www.crimestoppersvic.com.au.