MADRID, Spain - A Spanish court on Tuesday opened a manslaughter probe into a deadly fire that killed 13 people inside a nightclub which had ignored an earlier closure order.

The court in Murcia, where the blaze broke out early Sunday, said it had opened the investigation to "clarify the facts and determine criminal responsibility" for the blaze, Spain's deadliest nightclub fire in three decades.

The fire erupted just before dawn in a warehouse housing two discos, Teatre and Fonda Milagros, located on the outskirts of the city in southeastern Spain.

Police and forensic investigators entered the premises on Monday to try and determine how the fire started and whether it was the result of negligence.

The court said forensic medical teams had on Monday "completed the autopsies, collecting the necessary data for identification and determining the causes and circumstances of death".

Family and friends had submitted genetic samples the forensic teams were awaiting the results "to finalise the identification of the dead," it said.

The investigation will need to determine if the nightclub operators failed to take adequate safety measures, the city's top prosecutor Jose Luis Diaz Manzanera told La Opinion de Murcia newspaper.

If the deaths were caused by negligence or inadequate safety measures, those responsible could face up to nine years in jail "as it is a case involving a large number of deaths", he said.

Any search of the venue would be "exhaustive" to gather as much evidence as possible.

"We must go centimetre by centimetre, checking everything," he said.

"Let's see how it ends up. There may have been a short circuit that was not caused by negligence," he said.

Hiding in loos

Local firefighter Juan Angel Navidad said six of the bodies were found in the bathrooms, while the rest were found on a mezzanine-style balcony area above the entrance hall.

"It's possible some people hid in the bathrooms to protect themselves from the smoke," he told Antena3 television, saying one of the bathroom walls had collapsed.

He said firefighters initially found four people there, then later discovered two more under the rubble of the collapsed wall.

City officials had on Monday said that the venue, which was popular with Latin Americans, had been slapped with a closure order in January 2022.

The order, which they said was ignored, was issued after Teatre's management divided the venue in two to create a second club called Fonda Milagros, which bore the brunt of the blaze.

Officials did not say why the venue was still operating but said the fire appeared to have spread rapidly through the air conditioning vents.

Identifying victims 'very difficult'

By Monday night, police confirmed six of the victims had been identified by their fingerprints in what officials warned would be a "very difficult" process which would take time.

Relatives of the victims have been handing over to police personal items belonging to their loved ones such as toothbrushes or combs that can be used to provide DNA samples to help in the identification.

"No father or mother can, or should, have to go through a tragedy like this," Prime Minister Pedro Sanchez said Tuesday, adding the witness accounts of what happened are "heart-breaking".

"All of Spain feels the pain of the victims and their relatives and loved ones."

Diaz Manzanera said he hoped the outcome of the probe would not be the same as that which followed Spain's worst-ever nightclub fire in Madrid in December 1983, when 81 people died.

Only one person was sentenced over that tragedy, and jailed for just two years.

The latest blaze is the worst nightclub fire since 1990 when 43 people died in a blaze in the northeastern city of Zaragoza.

In that case "no one was held responsible", he added.