This comes after Prime Minister David Cameron announced the UK would take 20,000 Syrian refugees in the next five years.
May told MPs: “I know that honourable members and the general public are keen to know more detail on the numbers and when people are expected to arrive.
But I must underline that the scale of the expansion needs careful and meticulous planning to ensure we get it right.
The refugees will come directly from camps in Syria, so as to dissuade people from taking the “perilous” journey across the Mediterranean.
A total of 432,761 refugees and migrants have crossed the Mediterranean in 2015, more than doubling the total for 2014, the International Organisation for Migration said last week.
However, the UK will not take part in a proposed EU-wide resettlement scheme for refugees who have already arrived in Europe.
Earlier today it was reported tear gas was used against refugees at the Hungarian border, which has been widely condemned by other European nations, after having deployed a razor wire fence along its border with Romania and Serbia earlier this week.