Melissa Fleming, spokeswoman for the UNHCR, told reporters in Geneva that 336 male evacuees aged between 15 and 55 had been taken in for questioning.
A total of 42 were released, but the remainder were still in the hands of the authorities, she said.
They were being held at a school near Homs. UNHCR staff were at the building but not present during the interrogation sessions, Fleming said.
After the questioning, however, the aid workers were able to speak to the men, who said they wanted to be allowed to join the women and children who have already been evacuated.
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Its symbolism as a birthplace of the revolt against Assad put it sharply in focus during a first round of peace talks in Geneva between the regime and rebels last month.
An agreement that the civilians could be evacuated and aid brought in was the only tangible result of the talks, a second round of which began yesterday.
The regime has said it was essential to interrogate men in order to weed out "terrorists"- it says the revolt is fuelled by foreign jihadists and Gulf money.
But the opposition raised fears that separating the men of Homs from women and children could be a tactic to detain them.
The UN's humanitarian coordination office said today that a total of 1,132 people had so far been evacuated from Homs, but did not say how many people were thought to remain in the besieged districts.
In addition, there were 20 pregnant women among the evacuees.
UNICEF said that people emerging from the besieged areas spoke of a daily ordeal of cold, hunger, filthy drinking water and bombardment.