FBI Director Christopher A. Wray, center, prepares to testify before the Senate Homeland Security and Governmental Affairs Committee on Sept. 27. At left is Elaine Duke, the deputy secretary of homeland security, and at right is Nicholas Rasmussen, the director of the National Counterterrorism Center. (Melina Mara/The Washington Post)

The FBI is conducting about 1,000 investigations of suspected white supremacists or other types of domestic terrorists who might be planning violence, top federal officials told Senate lawmakers Wednesday.

Christopher A. Wray, in his first congressional testimony as FBI director, confirmed that his office has about 1,000 inquiries that people generally categorize as "domestic terrorism'' — a catchall term often used to describe those motivated to commit violence in furtherance of racist causes.

Sen. Ron Johnson (R-Wis.), chairman of the Senate Homeland Security and Governmental Affairs Committee, prompted Wray to confirm the number. FBI officials have previously said they had about 1,000 ongoing investigations in the United States of suspects who may be inspired by the Islamic State terrorist group to commit violence.

Wednesday's hearing was the first public indication that the FBI is dealing with a similar number of domestic terrorism cases.

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"We're very busy,'' Wray said. Asked by Johnson if there are any differences in how the FBI handles white supremacist terrorism cases vs. Islamic State terrorism cases, he said there are not, except for the criminal laws that may be applied.

Federal law makes it a crime to provide material support to a foreign terrorist group. There is no corresponding law regarding support for a violent white supremacist group.

"In most ways they're similar, probably the biggest difference is there's not a domestic terrorism offense as such,'' Wray told the committee. He added that investigations of foreign-inspired suspects also may use foreign intelligence court orders to gather intelligence — a tool that is not available in an investigation of a white supremacist group.

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The debate about the lack of such a law heated up after a suspected white supremacist drove his car into a crowd of protesters in Charlottesville this summer, killing a woman. He is awaiting trial in state court on murder charges.

Under questioning from lawmakers, Wray did not take a position on whether a law should be passed to make it easier to charge domestic terrorism cases.

He said he is concerned that would-be terrorists will try to use drones to conduct attacks in the United States, as they have overseas. And he said the battlefield defeats of the Islamic State group in Iraq and Syria mean that some suspects who would otherwise have tried to travel to those countries to join the group have decided to "stay put'' for the time being in their own countries.

Wray became FBI director in August after President Trump fired James B. Comey in May.