With the fire occurring during the First World War, rumours began to circulate a German arsonist had started the blaze, the "Toronto Globe" asserting that while the official cause of the fire was reported as a carelessly left cigar, "unofficial Ottawa, including many Members of Parliament, declare 'the Hun hath done this thing.'" Reconstruction of the Centre Block began immediately, with a team of architects led by John A. Pearson and Jean-Omer Marchand overseeing a design much like the original, but expanded in size and pared down in ornament, more in keeping with the Beaux-Arts ethos of the time. By 1 September 1916, less than seven months after the fire, the original cornerstone was relaid by the then governor general, Prince Arthur, Duke of Connaught and Strathearn, exactly 56 years after his brother, the future King Edward VII, had done the same. The new building was to be constructed with a steel frame, and an interior predominantly finished in stone, as well as with a more logical layout and clear exiting strategy. During reconstruction the House of Commons and Senate sat at the Victoria Memorial Museum Building. On 26 January 1920, the first sitting of parliament in the new Centre Block was opened by Governor General the Duke of Devonshire. However, the ceremony was also exceptional for the fact that it took place in the House of Commons, rather than the Senate, as the latter had not yet been constructed. Similarly, the corridors and main chambers were still devoid of their decorative carvings, which would be completed over the ensuing fifty years, and it was not until Dominion Day of 1927 that the Peace Tower was dedicated by Governor General the Viscount Willingdon. On 18 May 1966, Paul Joseph Chartier killed himself as he left a Centre Block washroom by accidentally detonating the bomb he had been preparing to throw onto the floor of the House of Commons from the public galleries to, as he put it in his notes, "exterminate as many members as possible." The building's security was heightened; however, tests of this by journalism students that November proved the precautions had been little improved. Later, in 1989, Charles Yacoub hijacked a Greyhound Lines bus and drove it up onto Parliament Hill. By the 1990s, it was deemed necessary for an upgrade to be made to the Centre Block's mechanical and electrical systems, which would necessitate a new plant for these amenities. To avoid disturbing the building's heritage façades and spaces, as well as erecting new structures within the parliamentary precinct, the two storey, square plant and new loading docks, called Centre Block Underground Services (CBUS), were constructed underground, seeing, in 1997, the removal of of rock from under and near the Centre Block.