The Victorian government has announced another 27 units will be installed by August at two correctional facilities near Geelong, a gain of 81 medium-security beds.
"Relocatable units are already providing an important, immediate boost to capacity in Victoria's corrections system, and today's announcement will build on this," Corrections Minister Edward O'Donohue said on Wednesday.
"The security and design of the units will be consistent with the standard security accommodation already at Fulham and Marngoneet prisons."
The government has previously likened the units - which each house three inmates - to mining camp accommodation and has also pointed to their use in prisons in Western Australia, South Australia and New Zealand.
Expansion plans for Victoria's Loddon Prison, announced in March, include 15 of the units.
The government says it has added 1000 prison beds since 2011 with another 2500 in the pipeline, including the 1000-bed prison under construction at Ravenhall in Melbourne's west.