FBI Director William Sessions says the agency expects to finish within a few weeks the first phase of a criminal investigation of the computer "virus" that attacked and disabled computer networks nationwide last week.

Sessions said Thursay the bureau is examining a wide range of possible criminal violations.A 23-year-old Cornell University graduate student has told friends he created the virus, a tiny program that spreads throughout computer networks and disrupts them.

Sessions, however, told reporters "there has to be a very careful and deliberate look at it before I would ever go out and suggest that a person had actually committed a crime."

"You have to move carefully, and I think we've done it properly in this case," he added.

Sessions said investigators are trying to determine whether statutes concerning wire fraud, malicious mischief or unlawful access to stored communications may have been broken.

Earlier this week, the FBI said it was focusing on a federal law that prohibits fraud or related activity in connection with computers, the Computer Fraud and Abuse Act of 1986.

Cornell student Robert T. Morris Jr. has told friends that he created the computer virus that disabled thousands of computers last week but didn't intend for it to spread as it did.

"We often look at intent as being knowing and intentional doing of an act which the law forbids and knowing that the law forbids it to be done," Sessions said. "But we also have other statutes which deal simply with knowingly doing something."