Yemen has detained 80 foreign students and teachers from an Islamic fundamentalist institute during a clampdown on illegal residents.
A security official says authorities are investigating whether the foreigners are in the country legally.
The detentions come near the end of a 30-day grace period for foreigners to legalise their presence in the country.
The detainees, mostly from Arab and south Asian countries, were studying and teaching at the private Dar Al-Hadith institute in the Marib province.
This is the same region where Yemeni special forces have been searching for al-Qaida terror suspects.
At least 34 people, including 18 soldiers, died last week in heavy clashes between Yemeni troops and Abida tribesmen suspected of harbouring the suspects.
It has not been confirmed if any of the men being held are thought to have links to al-Qaida.