"It is most of the international staff but local staff based in Maungdaw will still be there," he said, adding the voluntary measure was "temporary" and "because of the insecurity and disturbance".
A first group left Maungdaw on Sunday followed by a second group Monday.
UN workers are gathering in the state capital Sittwe, he said, and most will be flown to Myanmar's main city of Yangon. Workers for other non-governmental organisations have also been helped to leave the area, Nigam said.
Myanmar's government Sunday declared a state of emergency in Rakhine to deal with the violence.
The state, which is predominantly Buddhist, is home to a large number of Muslims including the Rohingya, a stateless people described by the United Nations as one of the world's most persecuted minorities.
Nigam said it was "a challenge" for staff to function normally in Maungdaw, which has been put under a curfew and where the United Nations has a humanitarian operation.