Rep. Jason Chaffetz, chairman of the House Oversight Committee, asked the State Department on Thursday for details of the relationships between Hillary Clinton's State Department aides and employees at the Clinton Foundation.

The Utah Republican raised concerns that the overlap between Clinton's diplomatic duties and the work of her family's foundation could have violated ethics rules that bar federal employees from using their positions for "private gain."

Among other records, Chaffetz requested "a list of all employees who sought leave, permission or ethics opinions in order to perform activities relating to the Clinton Foundation."

His letter to the State Department came amid renewed scrutiny of the Clinton Foundation stemming from a series of new documents that revealed the intimate ties between the charity and the federal agency.

For example, a set of call logs made public this week showed Cheryl Mills, then Clinton's chief of staff, spoke frequently by phone to foundation executives. An Associated Press review of documents obtained through a Freedom of Information Act lawsuit indicated Clinton reserved more than half of her non-government meetings for foundation donors.

Huma Abedin, then Clinton's deputy chief of staff, worked for both the Clinton Foundation at the State Department for several months in 2012 and 2013 in an employment arrangement that has piqued the interest of watchdogs and lawmakers. Mills reportedly helped the foundation interview candidates for a high-level position during her State Department tenure, a fact Chaffetz highlighted in his letter.

The potential conflicts of interest Clinton faced while serving as secretary of state have roiled her campaign this week, spawning criticisms that have only been made worse by her avoidance of a press conference for 263 days.