Undocumented Irish workers living in the US are being advised not to travel unless in absolute emergency, because they may be deported without proper identification papers.

Father Tom Flynn, chaplain at the Aisling Irish Centre in the Bronx, said yesterday there was a "significant number of undocumented workers" in the US, and despite economic circumstances in Ireland undocumented immigration "has been alive and active and well here in the past two or three years".

The Aisling Centre is encouraging people not to move around if they do not have the proper papers, because of the increased security. This call is echoed by the Emerald Isle Emigration Centre.

"The INS (Immigration and Naturalisation Service) has always been very effective at borders and now they have beefed up powers and regulations have been changed," said Ms Anne Marie Scanlon. "If they feel someone is not quite what they should be they have increased the detention period from 24 hours to 48 or 'a reasonable time'."

As the number of missing rose by 911 to 6,300, Irish organisations remained concerned about families who might be afraid to report a loved one missing because of adverse consequences. Father Flynn stressed that there would be no adverse reaction, and he appealed to families to come forward. He has evidence of three undocumented Irish people missing. "I have asked my source to go back to the families to encourage them to talk to us, but I have not heard anything in three days."

Three Irish tourists were reported to have been on the observation deck at the Trade Centre, but Ms Scanlon said there had been many rumours, most of them unfounded, and this highlighted the need for people to come forward.

The Irish consulate in New York says the number of missing is changing on a daily and even hourly basis. Currently, five Irish or first-generation Irish-Americans have been confirmed dead. A consulate spokesman said, however, that the Irish-Americans missing would be in the hundreds, including firefighters.