David Anderson, Britain's official independent reviewer of terrorism legislation, said he had asked authorities to explain why Miranda was detained and held for so long.
In most cases, those questioned under Schedule 7 are detained for less than an hour.
"It is such a wide power that it would be surprising if it was used perfectly on every occasion," Anderson told the BBC. "It is a very extensive power and this just points up the need to have it properly controlled."
Associated Press writer Bradley Brooks reported this story in Rio de Janeiro and Danica Kirka reported from London. AP writers Raphael Satter in London and Josh Lederman and Alicia Caldwell in Washington contributed to this report.