Cyber attacks have been waged against COVID-19 vaccine distribution infrastructure, including a cold-chain storage company, U.S. Senator Gary Peters said on Thursday.

“IBM recently released a very disturbing report detailing cyber attacks on COVID-19 vaccine distribution infrastructure,” Peters told a congressional hearing. “Just last month a cold-chain storage company also reported that they were the target of a cyber attack.”

Peters, a Democrat, made his remarks during a U.S. Senate Commerce Committee hearing on shipping procedures and capabilities for the vaccines, which are expected to start moving throughout the United States in coming weeks and months.

Richard Smith, a vice president at FedEx Express, said his company has been “hardening” its network to protect shipments from cyber attack but did not say whether it had experienced any problems.

Republican Senator Deb Fischer, who chaired the hearing, said IBM had identified phishing email attacks. She asked FedEx and United Parcel Service executives whether their companies or employees had been the target of cyber attacks.

Wesley Wheeler, president of UPS’ Global Healthcare, said, “We are not in a position to say that today,” but added that broadly, the company is the target of “attacks every day” and that it has an “incredibly tight email system.”