Steven Mark Herbert appeared in Muswellbrook Local Court on Monday on seven charges of taking part in the supply of prohibited drugs as well as one count of supplying on an ongoing basis - a charge that carries a maximum of 20 years imprisonment, if found guilty.

The 31-year-old was arrested on Friday by Oxley detectives in Muswellbrook following investigations by Strike Force Munderah.

The secret police operation unfolded last Thursday with seven others arrested in Gunnedah.

Magistrate Susan Horan denied Herbert bail on Monday, ordering him into custody, where he will remain while police compile the brief of evidence against him.

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He will return to court in May.

Oxley Detective Acting Inspector Jason Darcy said Oxley detectives also charged a Hunter Valley man at a correctional facility in Wellington on Monday.

The 31-year-old was charged with drug supply offences to front court at a later date.

"Investigations as part of Strike Force Munderah are continuing and further arrests are expected," he said.

On Friday, alleged ringleader Peter Joseph Lennan was denied bail in Tamworth court, a day after his arrest during a raid at a Baker Street home.

Strike Force Munderrah detectives, a covert police operation by Oxley detectives, alleges Lennan was the head of the criminal group and directed and coordinated his partner, Ricki Stranlund, and associates in methylamphetamine. 

Stranlund, 41, was in Tamworth Local Court on Friday in support of her long-term partner, after being charged and released on bail after her arrest on Thursday. She is facing charges of participating in a criminal group and ongoing drug supply. 

Peter Barnes was granted bail in the same court late on Thursday on drug supply charges. Four others were arrested and charged to front court at a later date.

Police allege the case against Stranlund and Lennan involved multiple drug transactions in August and September where methylamphetamine was sourced from the Upper Hunter area to return to Gunnedah to on-sell. 

"This extrapolates to more than 1,000 deals of methylamphetamine as each deal is approximately 0.1g in weight," police allege. 

In denying bail, magistrate Stephen Corry said it was a "strong prosecution case"; "it's almost inevitable", if found guilty, that Lennan "would be subject to a significant jail term"; and his "previous conviction for drug supply", and the ongoing allegation, meant that there "is a risk to the community of the defendant being at large". 

"For those reasons, bail is refused," he said.