Hackers linked to the Chinese government tried to steal research data related to Moderna’s (MRNA) COVID-19 vaccine candidate, Reuters reported Thursday. A U.S. security official said the breach occurred in January and targeted the Massachusetts biotech firm’s computer network.

The Reuters report followed an indictment of two Chinese nationals, Li Xiaoyu and Dong Jiazhi, last week by the U.S. Justice Department. They were accused of conducting “reconnaissance” against a U.S. company developing a vaccine for the novel coronavirus. The charges did not specify Moderna, but the details that were given in the indictments line up with Reuters’ information.

Moderna told Reuters it had been in contact with the FBI about a potential breach and was told it was carried out by the recently indicted Chinese nationals. 

“Moderna remains highly vigilant to potential cybersecurity threats, maintaining an internal team, external support services and good working relationships with outside authorities to continuously assess threats and protect our valuable information,” company spokesman Ray Jordan said in a statement.

Moderna’s vaccine candidate was one of the earliest in the U.S. to pick up steam and has received extensive backing from the federal government. A 30,000-person clinical trial is expected to begin within weeks.

“China has long been a major victim of cyberthefts and attacks,” China said in response to a Reuters inquiry. It said the country is “firmly” against any and all cyberattacks. This statement runs counter to a wealth of intelligence reports, indicating China regularly engages in espionage to steal research from overseas.