People living near the penitentiary in District 10 reported hearing a number of blasts from inside at around 7 p.m. on Tuesday, and shortly afterward seeing mobile and other police units arrive.

Around an hour later at least six blasts and a lot of screaming were heard.

More than two hours after that a truck left the prison with inmates followed by six more trucks carrying officers in protective gear.

A statement issued by the police at 1 a.m. Wednesday merely that when medical authorities performed checkups on inmates, "some incited others to scream and cause trouble."

They said some have been transferred to the T30 detention center in Cu Chi District, but did not provide a specific figure, to ensure distance between inmates to prevent the spread of Covid.

On July 3 a 26-year-old inmate, who had been imprisoned for trading narcotic substances, was taken to the April 30 Hospital managed by the Ministry of Public Security.

He died later that day and tested positive for the novel coronavirus.

In late June two male guards and a woman medical worker at the prison tested positive.

Chi Hoa Prison is an octagonal building spread over seven hectares with cells, watchtowers and lands farmed by the prisoners.

It was originally built by the French Indochina colonial government in 1943 to replace Maison Centrale at the corner of Ly Tu Trong and Nam Ky Khoi Nghia Streets.

It has for long been considered one of the most secure prisons in Vietnam with only two successful breakouts in its history.