Mayor Stephanie Rawlings-Blake announced Friday the hiring of a new chief technology officer to replace the official who resigned amid ethics concerns in February.

Chris Tonjes, the chief information officer for the District of Columbia Public Library, was chosen after a national search, the mayor's office said. He will start work July 23 in Baltimore.

"We are excited to announce the appointment of a qualified and forward-thinking individual to oversee an increasingly important government agency," Rawlings-Blake said in a statement. "Chris comes to us with years of experience as an innovator for one of the country's oldest public library systems. His understanding of the needs of a modern urban municipality will be critical as we develop strategies to make city government more effective and efficient."

In Washington, Tonjes oversaw the development of the first-ever iPhone application for a library, as well as iPad and BlackBerry apps. He implemented high-speed broadband for all library branches and led the effort to increase the number of public access computers by nearly 400 percent, Rawlings-Blake's office said.

Before working with the library, Tonjes was program manager for the district's Office of the Chief Technology Officer. He earned a bachelor's degree in English from the State University of New York at Potsdam in 1986, according to an online resume.

Tonjes will be replacing Rico J. Singleton, who resigned in February after an audit in New York detailed ethics violations while he worked in that state's government, including negotiating a job for his girlfriend and soliciting a job for himself with a software vendor that was awarded a major contract. His Baltimore salary was $160,000 — about $5,000 more than the mayor's salary.

Tonjes will receive $150,000. He did not immediately respond to a request for comment.

Tonjes takes over the Mayor's Office of Information Technology, an agency in the middle of a City Hall dispute. For weeks, Baltimore Comptroller Joan M. Pratt and Rawlings-Blake have sparred over the purchase of phone-related equipment by that office.

Pratt has said that the equipment purchases should have been subject to a separate competitive bidding process. The city solicitor, George Nilson, says the transactions were covered under a purchasing contract for computer equipment that did go through the bidding process. He has said the purchases were "neither out of the ordinary nor in violation of law."

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