The Scotland Yard investigation into alleged illegal payments by journalists to police and other public officials has been extended to Trinity Mirror and Richard Desmond's Express Newspapers, the Leveson inquiry has heard.

Deputy Assistant Commissioner Sue Akers, who is leading the Metropolitan police investigations into alleged illegal activity by journalists, said Operation Elveden, the probe into corruption, had gone beyond Rupert Murdoch's News International to include payments from other newspapers.

In one case a prison officer at a high security prison, who has now retired, had allegedly received payments from News International, Trinity Mirror and Express Newspapers totalling nearly £35,000, Akers told the Leveson inquiry on Monday.

She said the public official's former partner appeared to have facilitated the payments into their bank accounts, receiving "numerous payments" from NI, Trinity Mirror and Express Newspapers between April 2010 and June 2011.

She said further payments had been made after the official had retired, the last of which was by Express Newspapers in February 2012.

Akers said co-operation from News International's management and standards committee had enabled it to identity to which of the stories by News International papers the payments are believed to have been related.

"Further investigation has enabled us to identify stories in the Daily Mirror, Sunday Mirror, Daily Star and Star on Sunday that are suspected to be linked to the payments," she said in a statement to the inquiry.

Akers said the inquiry was also focusing on another public official, a prison officer at a separate high security prison, who allegedly received more than £14,000 from Trinity Mirror, publisher of the Daily Mirror, Sunday Mirror and the People, between February 2006 and January 2012.

The payments were also suspected to have been facilitated by the individual's partner, she said.

"Further inquiries have enabled us to identify stories in the Daily Mirror during the relevant period that are suspected to be linked to the payments," she said in a statement.

Akers said that it was the Met's assessment that "the majority of these stories reveal very limited material of genuine public interest".

She also said the police believed there were "reasonable grounds" to believe offences had been committed.

Letters were served on legal executives at both Trinity Mirror and Express Newspapers, publisher of the Star titles, on 11 July this year.

Akers said the letters requested "specific evidential material which Operation Elveden believed is in their possession and control and which is likely to be of substantial value to the ongoing investigation".

She said in her statement "the initial reaction from both newspapers was positive indicating co-operation with the police investigation".

Akers added: "The police intention has always been to go where the evidence takes us."

A Trinity Mirror spokesman said: "We take any accusation against the company very seriously and we are co-operating with the police on this matter. We remain engaged with the Leveson inquiry."

In January, the then Daily Mirror editor Richard Wallace told the inquiry that he was not aware of any payments to police, but that the paper had paid public officials connected to the health and prison services.

Asked by David Barr, counsel to the inquiry, about payments to prison officers, Wallace agreed that this information was confidential but argued that there was a public interest in the material being published.

He said: "By and large I believe there is a public interest in – if somebody is – from the hospital is saying, 'We have patients lying in the corridor, there's general chaos and here's some pictures, but I'd like some money for that', then you know, I'm quite happy with that because I think there's a strong public interest."

The inquiry has also received evidence from Desmond about alleged payments to police and public officials from his Daily Star titles.

Desmond said in his witness statement: "To the best of my knowledge, the newspapers have not used, paid or had any connection with private investigators in order to source stories or information and/or paid or received payments in kind for such information from the police, public officials, mobile phone companies or others with access to the same."

• To contact the MediaGuardian news desk email editor@mediatheguardian.com or phone 020 3353 3857. For all other inquiries please call the main Guardian switchboard on 020 3353 2000. If you are writing a comment for publication, please mark clearly "for publication".

• To get the latest media news to your desktop or mobile, follow MediaGuardian on Twitter and Facebook