The head of the Mayor's Office of Information Technology has resigned amid an investigation into allegations that the department paid contractual employees for work they may not have performed.

Christopher Tonjes, who denies any wrongdoing, expressed frustration in his resignation letter with the pace of the investigation.

"Having been arbitrarily placed on administrative leave amid a cloud of scrutiny, I have been unable to do my job and serve the citizens of Baltimore," Tonjes said in his letter to the mayor, submitted Monday. "Neither my career accomplishments, nor my unblemished record of public service, nor the undisputed fact that I have not engaged in any wrongdoing have brought this never-ending investigation to a close."

Tonjes said the investigation by Inspector General Robert H. Pearre Jr. "once promised to last weeks, has dragged on for months." He said he has not been interviewed by Pearre, despite offering multiple times to meet with him.

Mayor Stephanie Rawlings-Blake ordered an investigation in mid-March into what she called "very serious allegations of fraud and abuse."

Reached by phone Monday by The Baltimore Sun, Tonjes said, "I'm grateful that the mayor gave me the opportunity to serve. I look forward to reading about the fantastic work the administration is doing in the future." In his letter, Tonjes said he was "unwilling to become a distraction to the vital work that needs to be done in this city."

The inspector general's office did not respond to a request for comment.

Rawlings-Blake said in a statement that she accepted Tonjes' resignation and praised his deputy, Jerome Mullen, who has been serving as acting chief.

"Jerome has been a very capable partner these last several weeks while the Inspector General conducts his work to determine if there was any fraud or abuse within MOIT," the statement said. "Under Jerome's leadership, I am confident MOIT can move forward in supporting several priority initiatives ... including the modernization of our Police Department to help make Baltimore City safer as well as improving overall efficiency across city government."

The city's previous inspector general investigated irregularities in the information technology office under its previous director, Rico J. Singleton, who resigned in February 2012. Singleton stepped down after the release of a New York state audit found he had negotiated jobs for his girlfriend and himself while working for that state's information technology office.

The report by then-Inspector General David McClintock showed the office had purchased nearly $675,000 in phone-related equipment under an existing contract with Digicon rather than seeking new proposals. The scathing report found potential conflicts of interest and missed opportunities for "significant cost savings."

Tonjes was hired in July 2012 after having served as chief information officer for the District of Columbia Public Library.

In March, a spokesman for Rawlings-Blake said the new investigation was launched after the mayor received reports of potential improprieties. The investigation is centered on whether work that was supposed to have been done over the previous 18 months was completed, and whether it was done by the people who said they did it. Also, the probe will evaluate whether the work was done as efficiently as possible, according to a mayoral aide.

Three companies provided contractual workers during that period: Digicon, which has offices in Rockville and Virginia; Windbourne Consulting LLC, which has an office in Washington, among other cities; and Telecommunications Systems Inc., an international firm headquartered in Annapolis.

Windbourne Consulting and Telecommunications Systems Inc. are currently under contract to provide staffing for the city, said Kevin Harris, the mayor's spokesman. Digicon is not.

Council President Bernard C. "Jack" Young said Monday he was shocked by Tonjes' resignation. Young said he was pleased with the work Tonjes had done, calling him a "person who really understood the complex problems that we have with our system and was working toward fixing them."

Tonjes, who was paid $139,700 last year, was placed on administrative leave in March.

He said the decision to resign was difficult. During his time in the position, Tonjes said the office has revamped the city's 911 system to reduce the time emergency dispatchers need to answer calls, put agencies on an accelerated schedule for computer replacements, and entered a new leasing agreement with Microsoft to save the city $4 million over the coming years.

Tonjes said several of his projects are nearing fruition, including bringing WiFi to the Inner Harbor and a new billing system for water meters.

"I believe it is in the best interests of a city that I have grown to love so deeply," Tonjes said, citing the reason for his resignation.

Baltimore Sun reporter Luke Broadwater contributed to this article.

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