BAGHDAD — After a catastrophic fire in southern Iraq that killed at least 64 people, some victims’ relatives gathered in the holy city of Najaf on Tuesday to bury their dead, while dozens more were left waiting in limbo outside the wreckage of the hospital in a nearby city where flames swept through a coronavirus isolation ward the night before.

It was not immediately clear what caused the fire, at al-Hussein Teaching Hospital in Nasiriya, with health officials offering different explanations such as an electrical short or an exploding oxygen canister. Patients, relatives and health workers were among the dead from a blaze so intense that at least 22 of the bodies could not immediately be identified.

In late April, a similar fire at a coronavirus hospital in Baghdad, the capital, killed more than 80 people and injured more than 100. It was believed to have been caused by a spark igniting improperly stored oxygen canisters. Some of the patients hooked up to ventilators were burned alive in their beds along with visiting relatives who would not leave them. The hospital had no working fire alarm and no sprinkler system and Iraq’s health minister at the time resigned in response.

The two tragedies within three months were a reminder of the longstanding problems that have plagued Iraq’s health care system and other public services, which suffer from years of cumulative corruption and mismanagement. In many hospitals, visiting relatives crowd coronavirus wards and most lack procedures for properly storing oxygen cylinders or preventing or fighting fires.

President Barham Salih of Iraq, in a tweet, blamed the latest loss of life on “persistent corruption and mismanagement that undervalues the lives of Iraqis.” Prime Minister Mustafa al-Kadhimi ordered the detention of the provincial health director, the hospital director and the provincial civil defense director.

The city of Nasriya was a center of the protests that brought down Iraq’s government two years ago, and protesters rushed into the streets again after the fire on Monday night and into Tuesday, calling for the resignation of more officials.

The Iraqi civil defense chief, Maj. Gen. Kathem Bohan, said the building that housed the three-month-old coronavirus isolation ward next to the main hospital had been constructed from flammable materials. Other officials have said oxygen is stored haphazardly at almost all Iraqi hospitals.

Once the fire started, it spread with devastating speed and burned for three hours, according to witnesses.

On Tuesday morning, relatives were still combing through the charred rubble of the 70-bed facility looking for evidence of their missing loved ones.

At the scene of the fire late Monday night, civilians rushed to help rescue the wounded and to carry out the dead.

“When I arrived, the fire had completely engulfed the isolation ward,” said Ali Mahmoud, an unemployed engineer who put out Facebook messages calling for activists to help firefighters and rescue teams.

Mr. Mahmoud, 24, said he had helped carry out bodies.

Iraq is in the midst of a third wave of coronavirus infections. Last week, the country reached a high of 9,000 new cases a day with more than 17,000 dead since the pandemic began, according to the health ministry. The infection and death rates are believed to be significantly undercounted because many people believe it is safer to be treated at home.

Iraq, with its huge southern oil fields, is one of the biggest oil producers in the world. But because of rampant corruption, government dysfunction and militia control, the south is the poorest part of the country.

Falih Hassan, Awadh al-Taiee and Nermeen al-Mufti contributed reporting.