这是个被动句型，通常出现在报道中，表示据说什么什么，可以拓展出很多语法点
报道中通常用被动语态来表达人们说什么想什么，特别是当被报道的对象并不重要的时候
例：People in the area have been told that they should stay indoors. （被通知的人不重要，用被动）
对非特定人群的另一种常用报道形式是it+动词被动+that从句，重要的信息放在句末。这类动词有：report, allege, announce, assume, believe, calculate, claim, consider, demonstrate, discover, establish, estimate, expect, feel, find, know, mention, recommend, reveal, say, show, suggest, suppose, think, understand, agree, decide, hope, intend, plan, propose.
例：It is reported that the damage is extensive. （主动句型为The damage is extensive, according to government sources.长且累赘，报道主体不重要，重点是受损程度）
需注意不是所有的动词都可以采用第2点句型，不能用第二点句型的动词有inform, encourage, persuade, reassure, remind, tell, warn，这个时候它们需用第1点句型。
例：We have been informed that we have to leave. （不能用It has informed us...）
如果要突出主题，It+动词被动+that clause可以变型为主语+动词被动+to do。第2点里大部分动词都可以这样转换，除了announce, decide, mention, propose, recommend, suggest这些动词不可以
例：It is reported that the damage is extensive.
转化为 The damage is reported to be extensive.
tell译为命令的时候可以用第4点句型，但是译为说、告诉的时候不可以
例：I was told（命令）to go with them to the railway station.
不可以： The accident was told （说）to have happened just after midnight. （错误X）
某些发现类动词可以用it+动词被动+wh从句告知新发现或发生的信息，这类动词有discover, explain, find, know, reveal, show, understand.
例：It has now been revealed who was responsible for the accident.
当that从句的开头是that+there，可以转化为被动句there+动词被动+to be/to have been.
例：It is thought (that) there are too many obstacles to peace.
可转化为：There are thought to be too many obstacles to peace.
或者是：Too many obstacles are thought to be peace.
如 It is said that he is a scientist .
据说他是一位科学家。
放心采纳，谢谢