A laptop containing confidential information linked to the inquiry into the murder of loyalist paramilitary Billy Wright, has been stolen.
LVF leader Billy Wright was shot dead in the Maze Prison in 1997
The computer, belonging to a barrister who represents prison service staff in the inquiry, contains the details of a number of people in Northern Ireland.
The PSNI and the Crown Solicitor's Office are notifying them and assessing any implications of the theft.
The laptop was stolen from the barrister's office in London.
An NIO statement said the theft was being investigated by the City of London Police, in liaison with the PSNI.
It added that the secretary of state viewed it with serious concern.
DUP MP Jeffrey Donaldson said he was concerned about the theft and doubted whether paramilitaries were involved.
"Perhaps it involves people who don't want certain things coming out at the inquiry," he said.
"This was a very specific job, carried out by someone who had the task of going into the place and to remove the laptop."
Wright, the 37-year-old leader of the loyalist Volunteer Force, was shot dead inside the Maze Prison in 1997 by members of the republican Irish National Liberation Army.
Former Northern Ireland Secretary Paul Murphy announced the public inquiry into Wright's killing in November 2004 following allegations of security force collusion in his murder.
Meanwhile, the inquiry team has criticised the PSNI for failing to supply them with requested documents.
The panel said delays in obtaining documents from the security authorities have prevented the inquiry from getting under way, but it has decided to begin hearing witness evidence next week.
It has published a 75-page document highlighting the PSNI failures to supply information.
"The PSNI have suggested a number of reasons for any information gap that exists. Some of those reasons are referred to in this paper.
"They are not necessarily accepted by us."
The paper stated: "The chief constable of the PSNI has stated publicly on a number of occasions that his intent is to facilitate the work of the inquiry to the fullest extent possible.
"Despite this, the PSNI has been unable to provide the inquiry with a copy of documents it has requested."
Announcing they would begin to call witnesses, it added: "It may be that the panel will be provided with good explanations for the inability of PSNI to provide some of the materials that we seek and that, on any view, must have been within their record-keeping systems at some point of time."
The panel also expressed concern about a lack of hard-copy records held by RUC Special Branch.
It said they had been advised by the PSNI that Special Branch had stopped keeping hard-copy intelligence records from around 1994-95 and that all information from 1995 onwards was kept on computers.
Retired judge Lord MacLean is chairing the inquiry
However, it said the PSNI had been unable to come up with a single force order, internal memo, instruction or training material regarding the changeover from a written to a fully-computerised recording system for intelligence materials.
Inquiry chairman Lord MacLean told a brief public session in Banbridge, County Down, that the document on the PSNI failures contained "no direct or overt criticism" of the service. He said the PSNI would have the opportunity to respond.
In a statement, the PSNI said it was examining the report and remained "committed to fully cooperating with the inquiry".
"We have conducted exhaustive searches to deliver material to the inquiry, and a huge amount of effort and resources continues to be dedicated to servicing it," a spokesperson said.