Sudan's Foreign Ministry has permitted diplomats from Britain, Norway and South Africa to meet their nationals detained in a disputed region along the border with South Sudan.
Sudan claims the foreigners were carrying out military activities. They were arrested in the Heglig region, scene of recent fighting between Sudan and South Sudan.
The government used the arrests to back up its claims that South Sudan uses foreign fighters.
The diplomats said the group was in the region on a mine-clearing mission.
Foreign Ministry spokesman Obaid Ahmed Murawah said Monday the mine-clearing activities lacked government approval and should not be carried in an area "still in flames," a reference to the ongoing dispute.
He said the investigation is in progress.