Federal officials are on the lookout for four Pakistani nationals who are in the United States illegally after leaving a freighter that had been docked in Virginia sometime last weekend.

Immigration and Naturalization Service district directors and border patrol chiefs from across the country met on a "crisis management" conference call Thursday afternoon in which it was reportedly revealed that one of the four missing Pakistanis showed up on a "lookout list."  Since then, however, checks run on the Pakistanis suggest that they are on no such lists.

Some members on Capitol Hill who have heard about the case are "furious," according to sources, and the embarrassment is said to have further angered President Bush, who was put in another awkward situation last week when the INS mailed visa approvals for two Sept. 11 hijackers to the flight school they attended last year.

The latest incident prompted INS Commissioner James W. Ziglar to issue a memo to INS regional and district directors Friday evening warning that, effective immediately, he is "implementing a zero tolerance policy with regard to INS employees who fail to abide by headquarters-issued policy and field instructions."

"The days of looking the other way are over," he wrote.

The Coast Guard is distributing fliers in the Norfolk, Va., area of the missing crew members: Ahmad Salman, Thulan Qadar, Mohammad Nazir and Adnan Ahmad.

They were onboard the Progresso, a Malta-chartered freighter that was carrying a chemical commonly used in fertilizer, when it made port a week ago Friday near Norfolk from Novorossisk, Russia.

The ship has a 27-member crew; 19 are Pakistani. The captain is Croatian.

Last Friday, an INS inspector granted the four Pakistanis "shore leave visa waivers," which allowed them to come ashore even though they had not been granted visas for entry into the United States.

A list of crewmen was sent to INS a day before the ship arrived in Norfolk and INS screened the names. One of the missing crewmen had withdrawn a visa application to work on another ship several years ago in Chicago. That should have shown up when the man's name was checked on INS databases, but the agent entered the wrong birthday, a Justice Department official said.

The mistake was found after INS officials re-entered the information for the four men. The application withdrawal would not have prevented the man from getting the waiver, INS officials said.

One of the officials added, "None of them came up with anything terror- or criminal-related."

The names have also been run through a joint CIA-FBI counterterrorism database, an international criminal database managed by Interpol, and a French criminal database and no matches came up, according to INS spokesman Joe Karpinski.

However, the INS inspector violated INS rules, which prohibit Pakistanis from receiving waivers. After Sept. 11, the INS issued a directive specifically denying Pakistani crew members shore leave or "admission as crewman," which is offered to nationals from 29 mostly Western European countries with which the United States has specific reciprocal arrangements.

Pakistanis are also denied expedited processes and require extra scrutiny, according to INS directives.

All the men told the INS inspector that they did not have any family in the area and that they were veteran merchant mariners. The INS inspector could not electronically crosscheck the Pakistanis' identification while in the field.

Sources said that over the weekend, one of the men left while the ship was at a dock on South Military Highway in Chesapeake. Later, the ship moved to Triport Terminal, another facility a few miles down the southern branch of the Elizabeth River. Three more men left there.

Sunday afternoon, the captain reported to the INS inspector that the four Pakistanis had not returned to the ship. The Progresso then departed for Savannah, Ga.

The Associated Press contributed to this report.

Carl Cameron currently serves as Fox News Channel's (FNC) Washington-based chief political correspondent. He joined FNC in 1996 as a correspondent.