The number of new coronavirus cases linked to an outbreak at a detention center in southeastern Seoul has soared to over 700, with one inmate patient having died this week during treatment, according to the government Tuesday.

The Dongbu Detention Center found 233 more inmates were infected with the new coronavirus on Monday following its third mass testing, according to the Korea Disease Control and Prevention Agency (KDCA) and the justice ministry. The testing was conducted Sunday on 1,689 prisoners who had initially tested negative.

As of Monday afternoon, the number of patients tied to the prison outbreak reached 762. The figure included the number of confirmed inmates, employees, family members and acquaintances.

Virus transmissions tied to the detention center marked the single-largest outbreak incident at an institution level.

The inmates were put into cohort isolation in 15 buildings inside the detention center. The prison's medical staff will take care of patients who show no or light symptoms, while those with severe symptoms will be moved to hospitals, the justice ministry said.

One inmate who contracted the virus died Sunday while receiving treatment. After testing positive, the inmate had received care at a hospital outside of the detention center since last Thursday.

The inmate reportedly had underlying symptoms, having received hemodialysis treatment prior to contracting the virus. Health authorities are trying to find the exact cause of the death.

A group of 345 inmates who were earlier confirmed to have contracted the virus was transferred to a correctional facility in Cheongsong, about 320 kilometers southeast of Seoul, that day.

Elderly people and those with underlying medical conditions were excluded from the transfer.

The Cheongsong prison was chosen as a residential treatment center for coronavirus-infected prisoners with mild or no symptoms.

"In order to swiftly contain the situation in which cluster infections are breaking out consistently, (the ministry) plans to come up with additional steps to strengthen antivirus measures in consultation with health authorities," a justice ministry official said.

Justice Minister Choo Mi-ae inspected the outbreak response operation at the Dongbu Detention Center on Monday afternoon and asked employees to do their best to curb the spread of the virus.

The inmates, however, were apparently disgruntled at the justice ministry's response.

One inmate was seen holding a message on a piece of paper outside his prison cell at the detention center, complaining that eight patients were assigned to a single cell and that outbound letters were banned.

Earlier in the day, Prime Minister Chung Sye-kyun said he was "sorry for the mass outbreak at the detention center managed directly by the government."

"The possibility of additional community transmission is low, as most patients are inmates, but the number of patients could increase from additional mass testing," Chung said during a government meeting of top officials in charge of dealing with the pandemic. (Yonhap)