SAN FRANCISCO, Feb 16: Thousands of Muslim Americans and residents returning from the Hajj will face increased scrutiny at airports, with US officials putting special emphasis on centres with large Muslim populations like Detroit, Los Angeles, New York and San Francisco.

US officials said they are prepared to search and question thousands of Muslims travelling from the Middle East who are expected to begin arriving soon.

They warned that waiting times to get through Customs and Immigration and Naturalization Service inspections may increase.

Civil rights groups are concerned that the Muslims returning from the Hajj will be harassed, detained or barred entry.

Just before the event, the Council on American-Islamic Relations (CAIR), issued a travel advisory to American Muslims urging them not to travel outside the country unless absolutely necessary.