The ACT Government has expanded its overflow jail, with Canberra's prison once again reaching capacity.

Last month, the Government began moving prisoners to the Symonston Correctional Centre, as the Alexander Maconochie Centre (AMC) neared capacity.

ACT Corrections Minister Shane Rattenbury has previously stated that a maximum of 22 prisoners would be moved to the Symonston Correctional facility when needed, but today he said an extra eight beds would be made available.

The Symonston centre has been used as a weekend detention centre, but the ACT Government recently spent about $60,000 upgrading the temporary facility for full-time detainees.

There were 374 prisoners in the Alexander Maconochie Centre over the weekend, which is the highest number recorded.

The jail was only built to accommodate 370 prisoners.

"While some detainees were held on remand over the weekend and some have since been released, the population pressures are not easing," Mr Rattenbury said.

"There's some suggestion that particularly around domestic violence, that the judges are more reluctant to give people bail, that more people are spending time in jail as a result of concerns in the domestic violence space.

"That's not a scientific analysis, but perhaps that's a sense of what's going on."

Mr Rattenbury said all jurisdictions were seeing significant increases in the number of inmates.

"In New South Wales they're in the process of recommissioning two jails that they had previously closed," he said.

"The decision to move more detainees to Symonston has not been taken lightly.

"However for the safety of staff, detainees and the good order of the ACT's correctional facilities it is important that we maintain manageable numbers within the AMC and this means moving additional detainees today."

Mr Rattenbury again stressed that prisoners transferred to the Mugga Way facility would be low risk and carefully selected.

"Residents can be assured that the Symonston Correctional Facility is a secure facility with a secure perimeter and CCTV surveillance and its use as a full time custody option is a temporary measure," he said.

In April ACT Corrective Services notified residents in the area via mail that the Symonston facility may be used to accommodate detainees on a full time basis.