Senior ministers are set to be hauled in front of a leak inquiry as the hunt continues for the source who gave away details of a highly sensitive National Security Council (NSC) meeting.
Members of the Cabinet are expected to be summoned for interviews over the course of the weekend, the Daily Telegraph reported.
There is continuing fury in Whitehall that the deliberations of the country's most senior security body were leaked.
The formal inquiry - headed by Cabinet Secretary Sir Mark Sedwill - was said to have begun on Friday as ministers and their aides were issued with questionnaires.
Recipients were required to explain where they were in the hours following Tuesday's NSC meeting when Theresa May was said to have given the green light for the Chinese tech giant Huawei to help build the UK's 5G communications network.
They were also said to have been asked to provide details of all mobile phones in their possession and whether they spoke to the Telegraph which carried the original report about the Huawei decision.
Sir Mark, who is also the National Security Adviser, was reported to have given ministers until Friday afternoon to comply with his inquiry.
All those attending the NSC meeting have agreed to do so, according to the Telegraph.
In doing so they were said to have effectively given Sir Mark's inquiry team permission to examine the record of their calls, as well as any messages sent by text, WhatsApp or other means.
Much of the attention has focused on five ministers who were said to have voiced objections to the Huawei decision - Home Secretary Sajid Javid, Foreign Secretary Jeremy Hunt, Defence Secretary Gavin Williamson, International Development Secretary Penny Mordaunt and International Trade Secretary Liam Fox.
'We need to get to the bottom of it' - former defence secretary Sir Michael Fallon on the leak
MPs were quick to link the leak to the manoeuvrings around the Tory leadership, with whoever was responsible hoping to burnish their credentials for being tough on China.
All five however have either publicly denied being the guilty party or let it be known through aides that they were not responsible.
Also present at the meeting were David Lidington, the Cabinet Office Minister and Mrs May's de facto deputy, Chancellor Philip Hammond, Business Secretary Greg Clark and Culture Secretary Jeremy Wright.
Much of the anger around the leak from the NSC - where ministers are briefed by the heads of the intelligence agencies, MI5, MI6 and GCHQ - reflects concern among MPs and officials that it could damage intelligence-sharing with key partners such as the US.
Some MPs have called for the matter to be referred to the police or for MI5 investigators to be brought in, amid concerns that conventional Whitehall leak inquiries have a poor track record of finding the culprit.