OTTAWA -- The federal privacy czar says hackers who attacked Canada's National Research Council infiltrated a system containing personal information.

The privacy commissioner's office says it was first informed of the breach on July 23 and further briefed on Monday -- at which point the exposure of personal data was confirmed.

Tobi Cohen, a spokeswoman for the office, says the attack appears to be a serious security issue, but the full extent of the impact has yet to be determined.

She says the privacy commissioner is following developments very closely due to the potential implication for personal information.

The federal government revealed Tuesday that the council's networks were the target of a cyberattack, resulting in the shutdown of the research agency's IT network for an extended period.

Canada has squarely blamed the intrusion on a highly sophisticated Chinese state-sponsored actor, but Beijing has denied involvement, accusing Canada of making irresponsible accusations.