Washington — Department of Homeland Security headquarters, several of its component agencies and the Department of Health and Human Services have been hacked as part of a wider breach of Microsoft's SharePoint service, according to multiple U.S. officials. 

Microsoft confirmed its software was targeted by Chinese actors who deployed ransomware on the file sharing and storage platform. 

"Microsoft has observed two named Chinese nation-state actors, Linen Typhoon and Violet Typhoon exploiting these vulnerabilities targeting internet-facing SharePoint servers," the company wrote in a earlier this week. Guo Jiakun, a spokesperson for China's Foreign Ministry, on Tuesday he was "not familiar with the specifics" of the cyberattack and accusations of Chinese culpability. 

Two sources told CBS News that SharePoint was unavailable for several hours Tuesday for users at the Defense Intelligence Agency. 

The National Institutes of Health was also impacted by the breach. NIH conducts biomedical research and studies infectious diseases. 

A White House official said the White House is "closely monitoring the situation," and that the government "acted very quickly to immediately identify and mitigate this hack."

"We are working with all agencies to patch vulnerabilities and mitigate impact," the official said.

DHS spokeswoman Tricia McLaughlin said the Cybersecurity and Infrastructure Security Agency "quickly launched a national coordinated response through an initial alert and two cybersecurity updates" when the vulnerability was detected last Friday.

"CISA has been working around the clock with Microsoft, impacted agencies, and critical infrastructure partners to share actionable information, apply mitigation efforts, implement protective measures, and assess preventative measures to shield from future attacks," McLaughlin said, adding that there is "no evidence of data exfiltration at DHS or any of its components at this time."

Microsoft has issued a software update to patch the vulnerability. 

In April, President Trump fired General Timothy Haugh, the head of the National Security Agency and Cyber Command. 

Paulina Smolinski contributed to this report.