Home Minister Rajnath Singh on Tuesday said he didn't know why then home secretary L.C. Goyal was removed.Talking to the reporters on Tuesday, Singh said: "I don't know why he (Goyal) was removed."Goyal, a 1979 batch IAS officer, had sought voluntary retirement on August 31. It was approved by Prime Minister Narendra Modi.Rajiv Mehrishi, who was serving as secretary to the department of economic affairs under the finance ministry, replaced Goyal as the home secretary.