A Camperdown district man is currently under police guard in a Melbourne hospital waiting to be interviewed over a Cobden service station armed robbery.

Detective Senior Constable Jo Fisher, of the Warrnambool police crime investigation unit, said the 34-year-old man was under police guard in The Alfred hospital.

"He's the second person we were seeking to interview over the armed robbery committed at the Cobden BP Roadhouse on Monday morning last week," he said.

"It's understood that the man suffered injuries during a separate and unrelated vehicle accident."

It is not known when the man will be interviewed or if he will be charged in relation to the service station armed robbery.

On Sunday police said they were seeking to arrest and interview a second man.

He is well known to police.

Bacchus Marsh man Mitchell Darkes, 28, was arrested on Tuesday last week and charged with the armed robbery after forensics linked him to a vehicle seen just before and just after the hold-up at the Cobden BP Roadhouse at 8.15am Monday.

He was already on bail charged with committing a separate armed robbery and will be held in custody until a mid February court hearing.

At Sunday, 7.20am:

Warrnambool police detectives are seeking to arrest and interview a second man in relation to an armed robbery committed at a Cobden service station earlier in the week.

Detective Sergeant Andrew Raven, of the Warrnambool police crime investigation unit, said investigators believed the man would be able to assist them with their inquiries.

Bacchus Marsh man has been remanded in custody until February 19 next year charged with committing an armed robbery on Monday at a Cobden service station.

Bacchus Marsh man Mitchell Darkes, 28, was arrested on Tuesday and charged with the armed robbery after forensics linked him to a vehicle seen just before and just after the hold-up at the Cobden BP Roadhouse at 8.15am Monday.

He was already on bail charged with committing a separate armed robbery and will be held in custody until the mid February court hearing.

On Tuesday afternoon:

A 28-year-old Bacchus Marsh man has been remanded in custody until February 19 next year charged with committing an armed robbery on Monday at a Cobden service station.

Mitchell Darkes has been charged with breaching his current bail conditions, which relate to an armed robbery charge, and a new count of armed robbery, allegedly involving the Cobden BP Roadhouse at about 8.15am Monday.

Lawyer Brett Barratt said custody management issue included Mr Darkes suffering from a post traumatic stress disorder and an antisocial personality disorder.

He confirmed his client had been in custody previously.

Mr Darkes did not appear in court for the filing as he was being aggressive in the Warrnambool police station cells.

There was no application for bail.

Magistrate Mark Stratmann ordered forensics be conveyed to the appropriate facility for testing within 14 days.

A police brief of evidence service date was set for January 7, with a committal mention scheduled for February 19.

Mr Darkes was remanded in custody until February 19.

At 11.40am:

A 28-year-old Bacchus Marsh man is now being charged with an armed robbery at the Cobden BP Roadhouse service station.

Warrnambool crime investigation unit detectives have confirmed forensics have linked the man to a vehicle seen just before and just after the hold-up at 8.15am Monday.

The suspect was arrested early Monday afternoon at an address in Gunner Street, Camperdown.

It's understood the man was already on bail after previously being charged with a separate armed robbery.

He will appear in the Warrnambool Magistrates Court on Tuesday afternoon for a bail/remand hearing.

He is not expected to apply for bail

Tuesday, at 8.30am:

A 28-year-old Bacchus Marsh man has been remanded in custody overnight Monday on bail offences after being arrested in relation to an armed robbery in Cobden.

Detective Sergeant Andrew Raven, of the Warrnambool police crime investigation unit, said the man was arrested early Monday afternoon at an address in Gunner Street, Camperdown.

It's understood the man was already on bail after previously being charged with a separate armed robbery.

Police allege he was breaching his bail by being in Camperdown and not living at his Bacchus Marsh address.

"The man was arrested for the armed robbery, but has not been charged with committing the armed robbery, at this stage," Detective Sergeant Raven said.

"He's been charged with bail offences, was remanded in custody overnight and will appear in the Warrnambool Magistrates Court on Tuesday for a bail/remand hearing."

An armed robbery was committed at the Cobden BP Roadhouse service station about 8.15am Monday when an offender produced a large knife and demanded cash.

"The man in custody has made full denials in relation to allegedly being involved in that offence," Detective Sergeant Raven said.

"The offender demanded cash and was handed the float. It was early in the morning and they had just started business for the day. It was not a large sum of money."

Detective Sergeant Raven said it was a frightening experience for the three workers at the roadhouse.

"There was a cashier and two women working in the kitchen," he said.

"The offender has jumped on the counter and produced a large knife while making demands for cash.

"It was a terrifying ordeal for the three workers," he said.

Monday: A 28-year-old Bacchus Marsh man is being interviewed by police after an armed robbery on Monday morning at a Cobden service station.

Camperdown police Senior Sergeant Bill Caldow said a man entered the BP Roadhouse service station on the Camperdown-Cobden Road at 8.15am.

The man produced a large knife, which he pointed at a store attendant.

The offender demanded cash, jumped the counter and then made a further demand for cash from up close.

The man moved towards the cash registered and was handed a small sum of money by the store attendant.

The offender was wearing a mask and hoodie and ran from the shop heading south-west.

Police were notified and uniform officers attended from Camperdown, Cobden, Port Campbell and Mortlake as well as detectives from the Warrnambool crime investigation unit.

Late Monday morning the 28-year-old man from Bacchus Marsh was arrested at a Camperdown caravan park.

He is currently being interviewed by detectives.

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