WASHINGTON — The number of mentally ill people named in a federal database barring them from buying guns has more than doubled since the Virginia Tech shootings earlier this year, the Justice Department said Thursday.

The increase follows stepped-up reporting to a federal database used to screen the backgrounds of potential gun-buyers.

Attorney General Michael Mukasey announced the increase at an afternoon speech in Park City, Utah. The number of people identified in the national instant background check database as having mental problems grew from 174,863 three months after the April 16 Virginia Tech shootings to 393,957 this month.

“As the Virginia Tech tragedy made clear, it is vital that (the database) have accurate and complete information on persons prohibited from possessing firearms because of mental health history,” Mukasey told the National Association of Attorneys General. “Several states have begun submitting records that previously had not, or have worked to increase the number of records they submit.”

In his first policy speech since being sworn in as attorney general earlier this month, Mukasey said he hoped more states will submit the names.

People are included in the federal database only after courts or other lawful authorities have found them to have mental health problems, Justice Department officials said. Currently, 32 states, including Washington, submit names to the mental health database, and the federal government cannot force the other 18 to follow suit.

Virginia Tech student Seung-Hui Cho killed 32 people and himself in the deadliest shooting rampage in U.S. history. He bought two guns — a Glock 9mm at a Virginia store and a .22-caliber pistol over the Internet — despite a special justice’s 2005 order for Cho to get outpatient treatment for being a danger to himself. There has been no indication that Cho ever received the treatment.

Had his court order been submitted to the federal database, Cho likely would have been unable to legally buy the guns.

Private mental health records, including diagnosis documents from hospitals or insurance companies, are not reviewed or submitted to the database. Overall, more than 5 million people are identified in the background check system that is maintained by the FBI and also tracks the names of illegal immigrants, domestic violence offenders and others who are barred from buying guns.

Despite Cho’s gun purchases, Virginia traditionally has submitted far more names of mentally ill people to the federal database than other states, Justice data show. Shortly after the Virginia Tech shootings, officials said the state had given 81,233 names to the FBI. Michigan had the second-largest submission of names then, with 73,382, according to Justice data.

By comparison, California had submitted only 27 names of mentally ill people to the database as of April 30. Since then, the state has given more than 200,000 names to the list, Justice officials said.