A man takes pictures as Apple iPhone 6s and 6s Plus go on sale at an Apple Store in Beijing, China September 25, 2015. REUTERS/Damir Sagolj/File Photo

WASHINGTON (Reuters) - Four U.S. House Republicans, including the chairman of the Energy and Commerce Committee, on Friday wrote Apple Inc AAPL.O chief executive Tim Cook asking him to answer questions about its disclosure that it slowed older iPhones with flagging batteries.

The California-based company apologized over the issue on Dec. 28, cut battery replacement costs and said it will change its software to show users whether their phone battery is good. The letter also said they were concerned about reports that an iPhone battery overheated and began to emit smoke in Switzerland.

U.S. Senator John Thune, who chairs the Senate Commerce Committee, sent a similar letter to Apple on Tuesday. Apple did not immediately respond to a request for comment Friday.