XML declaration is repeated at the document

Hi,
   I am using c# open XML to write to excel. However, in the document. The XML declaration is repeated. What is the cause of this error and how to fix it?

<?xml version="1.0" encoding="utf-8" standalone="yes"?><x:worksheet
	xmlns:r="http://schemas.openxmlformats.org/officeDocument/2006/relationships"
	xmlns:mc="http://schemas.openxmlformats.org/markup-compatibility/2006"
	xmlns:x14ac="http://schemas.microsoft.com/office/spreadsheetml/2009/9/ac" mc:Ignorable="x14ac"
	xmlns:x="http://schemas.openxmlformats.org/spreadsheetml/2006/main"><x:dimension ref="A1" /><x:sheetViews><x:sheetView tabSelected="1" workbookViewId="0" /><?xml version="1.0" encoding="utf-8" standalone="yes"?><x:worksheet xmlns:r="http://schemas.openxmlformats.org/officeDocument/2006/relationships" xmlns:mc="http://schemas.openxmlformats.org/markup-compatibility/2006" xmlns:x14ac="http://schemas.microsoft.com/office/spreadsheetml/2009/9/ac" mc:Ignorable="x14ac" xmlns:x="http://schemas.openxmlformats.org/spreadsheetml/2006/main"><x:dimension ref="A1" /><x:sheetViews><x:sheetView tabSelected="1" workbookViewId="0" />

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