(CNN) Senate Homeland Security and Government Affairs Chairman Ron Johnson is joining the list of Republicans seeking interviews with the senior FBI and Justice Department officials at the center of the investigation into Donald Trump and Russia.

Johnson, of Wisconsin, told CNN Tuesday that he sent a letter to Attorney General Jeff Sessions listing senior FBI and Justice Department officials he wants to interview about the FBI's investigation into Trump and Russia — which has come under fire from conservatives who have questioned the genesis of the probe — as well the FBI's handling of the investigations into Hillary Clinton's email server and the Clinton Foundation.

Johnson's letter includes a request to speak with more than 30 current and former FBI and Justice Department officials, including former FBI Director James Comey, former Attorney General Loretta Lynch, former Deputy FBI Director Andrew McCabe, FBI agent Peter Strzok, former FBI attorney Lisa Page and Justice official Bruce Ohr, according to a source with knowledge of the letter.

The letter also includes a request to speak with FBI agents on Lynch's protective detail when she met Bill Clinton on a Phoenix airport tarmac, and FBI and Justice officials who worked on the Clinton email and Clinton Foundation investigations, including those who discovered emails on former Rep. Anthony Weiner's electronic devices, according to the source.

A Justice Department official confirmed that the department had received the letter, and declined to comment further.

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