Houston Chronicle reporter Mike Ward resigned from the outlet on Monday after allegations surfaced that he had made up sources for a number of stories.

Nancy Barnes, executive editor of the Houston Chronicle, issued a statement. In part, it reads:

“Recently, another Houston Chronicle journalist flagged me with questions about the accuracy of a story written by veteran Austin reporter Mike Ward. Ward joined the Chronicle in 2014 after a long career with the Austin American-Statesman. Specifically, questions were raised about whether individuals quoted in one of his stories were real people. Our own researchers, after an initial review, had difficulty finding a number of sources cited in Ward’s most recent reports. Ward has insisted that his work was truthful, that his work involved real people, and that we would eventually find the individuals behind his ‘man-on-the-street’ interviews. However, given the questions this review raised, he offered to resign and I accepted that resignation last week.”

The Houston Chronicle has hired an “independent, highly respected journalist” in an effort to investigate Ward’s alleged journalistic violations.

The investigator, Barnes says, has been given “full access to our archives and promised access to our editors as well.”

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