MIAMI - Dealing a blow to more than 200 Haitians detained in South Florida, the U.S. Immigration and Naturalization Service thwarted attempts by an immigration judge to grant bond yesterday to the migrants, charging that they pose a threat to national security.

Meanwhile, a federal judge ordered six Haitians held without bond on charges that they orchestrated last week's smuggling operation that ended with more than 200 Haitians jumping from a rickety wooden boat into Biscayne Bay and climbing onto the Rickenbacker Causeway.

Volunteer attorneys helping the migrants decried the 57 scheduled bond hearings - which were not announced - as an "ambush" to expedite the migrants' return to Haiti. Immigration Judge Scott Alexander set bond for more than 25 Haitians at between $1,500 and $4,500. More than 90 more hearings were scheduled for today.

The attorneys also criticized the INS for appealing the bond determinations, claiming the INS treats Haitians unfavorably compared with other migrants.

"It appears to be justice by ambush," said Randolph McGrorty, executive director of Catholic Charities Legal Services. "It was done too quickly. If this case continues, they will be deported and removed back to Haiti very quickly. I don't think they'll get a fair hearing."

Attorneys argued they had been denied access to the migrants, given limited hours to talk to them and little privacy. The Haitians called to the bond hearings yesterday were given Creole translation via telephone. Each hearing took about a half-hour.

"It's very disconcerting. You're in front of a judge in a courtroom, there's an INS trial attorney there and you're communicating with a box," said Cheryl Little, executive director of the Florida Immigrant Advocacy Center. The center has four volunteer attorneys working full-time on the cases.