It's been almost 19 months since Liam Payne's tragic death ... and a British coroner says he still doesn't have the evidence he needs to officially determine the singer's cause of death.

During a pre-inquest hearing Thursday ... Buckinghamshire, UK Senior Coroner Crispin Butler explained he hasn't heard anything from anyone in Argentina since the last hearing ... which was in January 2025.

He told Beaconsfield Coroner's Court ... "We have had no further disclosure of evidence from Argentina via the Foreign, Commonwealth & Development Office." Beaconsfield is a suburb of London, England.

During the last review -- more than a year ago -- Dr. Roberto Victor Cohen said Liam died from polytrauma ... meaning he died from multiple traumatic injuries.

But Butler said in that hearing it could still "take some time" before they could formally reveal Liam's cause of death ... and said he wanted full reports and eyewitness statements.

And now, Butler says he believes the investigation in Argentina is still ongoing ... hence the delay. He also noted that the documentation he got before the hearing had "undergone a process of translation."

He plans to pass those docs along to Liam's family ... who skipped Thursday's hearing. The next pre-inquest review won't be until December 1.

As you know, Payne fell to his death from a hotel balcony in Buenos Aires in 2024 ... and an autopsy performed in Argentina found drugs were found in his system.