Downing Street has said it is "categorically not reviewing" whether foreign students should be excluded from net migration figures.
The prime minister's spokesman clarified the government's position after earlier saying there would be an overall review of immigration policy.
The chancellor has suggested foreign students and highly skilled workers are not a major area of concern.
The government is committed to bring net migration down below 100,000.
But according to Office for National Statistics estimates, net migration to the UK, rose to 333,000 in 2015 - the second highest figure on record.
In evidence to the Treasury Select Committee on Wednesday, Chancellor Philip Hammond said decisions about what was covered by the net migration target should be guided by public perception - and suggested highly skilled workers could be exempt.
He told MPs: "When the public tells us loudly and clearly that they have a problem with levels of migration, it is very clear to me that they are not talking about computer programmers, brain surgeons, bankers, senior managers... possibly students.
"But they are talking about people competing for entry-level jobs with people in the UK who, perhaps, have a level of skills that means they only have access to those kind of jobs."
The prime minister's spokesman said earlier on Thursday: "The issue of migrant numbers that will come into the country, be it student or otherwise, is an issue that will have to be very closely looked at by the government as we set about establishing a new system."
But later in the statement, Downing Street said: "The government objective is to reduce annual net migration to the tens of thousands, and in order to deliver this we are keeping all visa routes under review.
"Our position on who is included in the figures has not changed, and we are categorically not reviewing whether or not students are included."
BBC political correspondent Alex Forsyth said Mrs May had consistently resisted calls to exempt international students from immigration numbers while she was home secretary and it appeared, as prime minister, she was doing the same. She added, following Mr Hammond's comments, it would be seen as further evidence of differing opinions within the cabinet about how to manage migration, after Brexit.