A statement from the ministry, giving an update on the H1N1 situation in Singapore, said all the close contacts were 'accounted for' by 3pm and home quarantine orders would be served on them.

The 10th flu case is a 33-year-old Singaporean woman who flew back on Singapore Airlines SQ25 from New York via Frankfurt and arrived in Singapore on Monday.

She was in the US from May 23 to 30 and was seated in row 19 on the SQ flight.

MOH has identified two close contacts on the flight and two close household contacts, all of whom will be quarantined at home.

The 11th flu case is a 19-year-old American student who arrived in Singapore on Monday to visit a relative. She was also on the same flight seated in row 57.

No contact tracing of flight passengers was carried out because the girl developed the onset of symptoms more than 24 hours after disembarkation.

But MOH has identified four household contacts and placed them on home quarantine orders.