The “troubling incident” of a senior coroner who lost a file with information on the murder of teenager Alice Gross is being investigated, the Ministry of Justice has said.

Coroner for west London Chinyere Inyama, who covers inquests from Richmond and Kingston, lost the file, reported in the Guardian as a 30-page document, in November last year, one month after the schoolgirl’s body was found weighted down in the Grand Union Canal.

It is believed Mr Inyama left it on a train.

The Metropolitan Police said, the file contained evidence against prime suspect Arnis Zalkalns, who killed himself before he could be arrested, and that is was likely “destroyed as waste”.

Alice’s mother and father, Ros Hodgkiss and Jose Gross, knew nothing of the matter until the story was reported in the Mail on Sunday.

They would later say in a statement: “We have looked to the police and coroner to help us through our awful loss.

“Yet now we learn they, either independently or together, have withheld from us the loss of this terribly sensitive information about Alice.

“We are extremely concerned, bewildered and angry, and we have asked for a full written explanation as to what exactly happened and why we were not told.”

Latvian Arnis Zalkalns, 41, murdered his wife in 1997 and was found hanged ahead of his arrest on suspicion of Alice’s murder.

A Metropolitan police spokesman said: “In November 2014 the MPS was informed by HM coroner, London west, that he had inadvertently disposed of a single document relating to the police evidence against Arnis Zalkalns. An investigation to recover it was undertaken. This concluded that it was highly likely it had been destroyed as waste.”

The Ministry of Justice said in a statement: “This clearly appears to be a troubling incident. A full investigation is now under way.”