a week later, and the injunction was reversed. Unlike at other projects, the groundbreaking ceremony was private, and the cornerstone only had the year "1907" inscribed in Roman numerals. During construction in 1911, a fire broke out on the 25th floor; at the time, it was the highest fire to date that the New York City Fire Department had fought. In another construction incident, three workers were buried when temporary bracing in the foundation collapsed, though all survived. Steel frame construction took place between June 1910 and July 1911, followed by the installation of exterior walls between March 1911 and November 1912. There were delays in installing the granite facade because the original materials were found to be inferior. By 1913, the superstructure was topped out with the unveiling of Civic Pride at the top of the Municipal Building's tower. Use 1910s and 1920s The first sections of the Municipal Building were occupied in mid-1913. The building had not been ready at the beginning of the year, forcing some city departments to renew the leases at their existing quarters. Mayor John Purroy Mitchel, after taking office in 1914, criticized the usage of space in the Municipal Building as "wasteful". Some of the city departments that were scheduled to move into the building had found space elsewhere, and other city departments had been allotted less space in the building than in their previous quarters. Two years later, the New York City Board of Estimate commenced an investigation into office vacancies at the Municipal Building, after the New York Public Service Commission leased floors in other buildings. The building had cost $12 million (), which was not repaid with interest until 1964; the interest was more than twice the original cost. The land alone had cost $6 million. Nevertheless, the structure was expected to save the city from paying $800,000 a year in rent. Upon opening, the Municipal Building housed 4,200 city employees. It was patrolled by a private police force, which monitored the building 24 hours a day, as well as a cleaning crew of 135 people. There were also telephone switchboards for inter-departmental communication, which at the time of completion were described as state-of-the-art. A nonprofit organization established a cafeteria on the 26th floor in 1918; although the city provided no subsidies to the cafeteria, the cafeteria also did not have to pay rent. Radio station WNYC (AM) started broadcasting