Security guards were reportedly overpowered by the inmates and were forced to open the main gate to let them out.
According to media reports, police have so far recaptured 332 of the escapees and are continuing to search for the 230 others.
The centre accommodates 1,481 inmates.
Under Vietnam law, homeless drug addicts or any user who relapses after receiving outpatient treatment must receive a mandatory two-year rehab sentence.
Conditions in the country’s rehab centres have been condemned by the US-based Human Rights Watch group, which says they should be closed.
There are an estimated 200,000 drug addicts in Vietnam, many of them heroin users.
– TiVi Tuan-san