Mourners have been warned by the Department for Digital, Culture, Media and Sport (DCMS) not to attempt to join the queue at Southwark Park in south-east London until around 4pm on Friday at the earliest.
The call was made as the official estimate for queuing time reached at least 14 hours.
However, there was some confusion on the ground as hundreds of people continued to file through the gate into the park, with one attendant saying they had yet to receive an order to bar entry.
The DCMS had tweeted: “Southwark Park has reached capacity. Entry will be paused for at least 6 hours. We are sorry for any inconvenience.
“Please do not attempt to join the queue until it re-opens.”
Tens of thousands of people have queued for many hours to see the monarch’s coffin raised on a catafalque in Westminster Hall since it officially opened on Wednesday.
With people waiting through the night to witness the lying in state, the queue had grown to almost five miles long by Friday morning.
The Government had warned that Southwark Park had become “extremely busy” before making the decision to suspend entry.
But hundreds of mourners were witnessed continuing to enter the park despite the Government’s online warning.
One queue attendant told the PA news agency they had yet to receive any instructions to close the gate and stop any more people joining.
The lying in state will be open 24 hours a day until closing at 6.30am on Monday, ahead of the state funeral in Westminster Abbey.
Meanwhile, the King is to visit Wales for the first time since ascending the throne before returning to London to hold a vigil at the Queen’s coffin with his brothers and sister.
Charles and the Queen Consort are travelling to Cardiff on Friday for the next leg of a home nations tour following the Queen’s death, after trips to Northern Ireland and Scotland.
The King and Camilla will attend a service of prayer and reflection at Llandaff Cathedral before receiving condolences at the Welsh parliament, the Senedd.
He will later hold a private audience with Welsh First Minister Mark Drakeford and the presiding officer at Cardiff Castle, although a protest against the monarchy is expected outside.
Charles will then attend a reception hosted by the Welsh Government before returning to Buckingham Palace in the evening to host faith leaders in the Bow Room.
Some of those who manage to enter the queue will witness the King, the Princess Royal, the Duke of York and the Earl of Wessex as they hold a 15-minute vigil around the coffin at 7.30pm.
The Prince and Princess of Wales are due to visit Army Training Centre Pirbright in Surrey to meet troops from the Commonwealth who are to participate in the Queen’s state funeral.
On Thursday, more details were revealed about the funeral, which will see 2,000 people, including world leaders and foreign royals, gather at Westminster Abbey on Monday.
Recipients of the Victoria Cross and the George Cross, and representatives of the Westminster Parliament, devolved parliaments and assemblies, the Church and Her Majesty’s patronages are among those who will also attend.
The service will be conducted by the Dean of Windsor, with Prime Minister Liz Truss and Commonwealth secretary general Baroness Scotland reading the lessons, and the Archbishop of Canterbury delivering the sermon.
Some 800 people, including members of the Queen’s Household and Windsor estate staff, will attend the committal service at 4pm in St George’s Chapel, Windsor Castle.