Meanwhile near Lebanon, Syrian forces and rebels clashed over the strategic town of Yabroud, causing hundreds of people to flee over the border.
The halt in evacuations came just a day after a cease-fire was extended for three more days. Hundreds more civilians are believed to still be trapped in a rebel-held medieval quarter known as Old Homs.
Senior Syria UN official Matthew Hollingworth told The Associated Press by telephone from Damascus that dozens of men and boys aged 15 to 55, who left Old Homs during earlier evacuations, are still being held and questioned by Syrian authorities.
The Syrian government considers males of military age to be potential combatants who must obtain security clearance before being released. Those authorities suspect of being rebels will likely be detained.
Hollingworth said several dozen men were being held in a school in Homs and that UN officials are also present there.