The FBI and Guyana police have questioned two Shiite Muslim leaders they say knew at least one of four Caribbean nationals arrested in an alleged plot to attack New York's John F. Kennedy International Airport.

The two unidentified Guyanese men — who were not arrested — also had been in contact with a confidential informant who is expected to be a main witness in the case, Guyana Police Chief Henry Greene said on Sunday.

The FBI and local police interviewed the two men last month and police say they plan to question other people who had contact with those involved in the case.

In June, three men were arrested in Trinidad and accused of participating in a Muslim terror cell that planned to bomb a jet fuel artery that runs through several neighborhoods and feeds the JFK airport. Abdul Kadir and Abdel Nur of Guyana and Kareem Ibrahim, of Trinidad, are expected to appeal an extradition order to the U.S. in the next two weeks.

A fourth suspect, U.S. citizen and Guyanese native Russell Defreitas, had worked as an airport cargo handler and is in custody in New York. U.S. authorities say he is the alleged mastermind of the plot, and claim that the alleged plotters unsuccessfully sought help in Trinidad from Jamaat al Muslimeen, a radical Islamic group that staged a deadly coup in 1990.

The four are charged with conspiring to cause death, serious bodily injury and extensive destruction. According to court documents, the men allegedly planned to seek Iran's help in a strike intended to dwarf the attacks of Sept. 11, 2001.