A ransomware attacked crippled the information technology systems at New Jersey’s largest hospital health network for nearly five days last week, a company statement confirmed Friday.

Hackensack Meridian Health initially declined to say what had caused its systems to malfunction, saying it was under investigation.

“Due to developments in the investigation, and on advice of national experts, we could not disclose that this was a ransomware attack until now,” the statement said.

“Our network’s primary clinical systems are operational, and our IT teams continue working diligently to bring all applications back online safely," according to the statement. "Based on our investigation to date, we have no indication that any patient or team member information has been subject to unauthorized access or disclosure.”

The attack affected “anything with computer software — scheduling and billing systems and labs and radiology," a hospital IT professional who works with Hackensack Meridian told NJ Advance Media last week. He said he was told a ransomware attack had been responsible.

The union Health Professionals and Allied Employees, or HPAE, also described nurses as “extremely concerned.”

“There have been delays in orders, lab work and they are having to double-check paperwork carefully to make sure everything is accurate," said Bridget Devane, the HPAE spokeswoman.

Hospital officials said at the time roughly 100 elective surgeries were rescheduled, but disruptions, due to the “externally-driven technical issues,” were minimal.

“Due to the extraordinary efforts of our physicians, nurses, and clinical teams, patient safety was not compromised. We apologize for any inconvenience this may have caused our patients,” the hospital’s statement said. “The safety and care of our patients remains our priority."

Hackensack Meridian’s statement said it holds insurance coverage for these emergencies, and declined to reveal how much it paid the hackers to regain control over its IT system.

Ransomware is malicious software, known as malware, that is usually sent under the guise of a legitimate-looking link or email attachment. If clicked or opened, the malware encrypts data on a computer system, often restricting access to the system until a ransom is paid. Hackers also threaten to compromise data in many cases unless the victim agrees to pay the ransom.

Ransomware attacks are on the rise.

Emsisoft, a cybersecurity firm, issued a report Wednesday on ransomware attacks in the U.S. in 2019, documenting 948 attacks against government agencies, health care service providers and school districts through the first nine months of the year.

Healthcare providers were the most frequent target, with 759 attacks, the report said.

“The incidents were not simply expensive inconveniences; the disruption they caused put people’s health, safety and lives at risk,” according to the report. “Emergency patients had to be redirected to other hospitals, medical records were inaccessible and, in some cases, permanently lost and surgical procedures were canceled, tests were postponed and admissions halted.”

Hackers attacked New Orleans city government on Friday.

Hackensack Meridian is a $6 billion nonprofit system operating 17 acute care and specialty hospitals, nursing homes, outpatient centers and the psychiatric facility Carrier Clinic.

Susan K. Livio may be reached at slivio@njadvancemedia.com. Follow her on Twitter @SusanKLivio. Find NJ.com Politics on Facebook.