At least 68 people have died after a massive fire engulfed the overcrowded holding cells inside a police station in northern Venezuela on Wednesday, officials said.

The country's chief prosecutor, attorney general Tarek William Saab, said on his official Twitter account that almost all the victims were male detainees. Two women who were visiting overnight were also killed, he said.

Four prosecutors have been designated to investigate the inferno at the Carabobo state police headquarters in Valencia, according to Saab. The cause remains unknown.

Relatives of detainees were seen gathering outside the station, anxiously waiting to hear the fate of their loved ones.

Carabobo state secretary-general Jesus Santander said in a press conference Wednesday that authorities were still working to ascertain the exact number of deaths. The interior ministry, as well as other agencies, will determine the cause of the deadly blaze, he said.

Santander promised that the local government will provide "comprehensive social assistance" to victim's families, including support for funeral services and psychological care.

"We extend our solidarity to the families of the victims, as well as the families of the detainees who are injured and those who are presently out of risk. The government of Rafael Lacava has instructed its team to tend to the families of all victims," Santander said in the press conference.

The United Nations Human Rights Office said it was "appalled at the horrific deaths," adding that it's "concerned at reports that security forces used tear gas to disperse relatives who had gathered in front of the police station in Valencia, Carabobo State, to demand information about their loved ones."

"There is widespread overcrowding and dire conditions in Venezuela’s prisons and also in police jails, which are often used as permanent detention centres. These conditions, which often give rise to violence and riots, are exacerbated by judicial delays and the excessive use of pre-trial detention," the statement continued. "... To this end, we urge the authorities to ratify the Optional Protocol to the Convention against Torture, so as to enable independent prison monitoring by an international body."

The devastating fire is emblematic of a larger issue facing Venezuela in recent years. As Venezuela's economy teeters toward collapse, many prisoners are starving and being kept in congested cells, according to the Venezuelan Prisons Observatory. Many prisoners are also being detained at police stations for much longer than the typical holding period of a couple days due to overcrowding at larger jails, according to Caracas-based watchdog group.

The International Monetary Fund projects the Venezuelan economy to decline another 15 percent this year, following a downward trend in the South American nation's oil exports due to its plummeting oil production. If the forecasts are accurate, then half of Venezuela's oil-dependent economy will have disappeared since 2014.