BUFFALO, N.Y. -- Two different sources tell 2 On Your Side that the virus that took down the computer system at the Erie County Medical Center (ECMC) was the result of "ransomware", although the hospital would neither confirm nor deny that.

For days, many experts have speculated that ransomware was to blame, based on the hospital's response, the length of time it's taken to repair the system and other factors.

Ransomware is when hackers get into a computer system and demand money. One source said the ransom at ECMC was in the tens of thousands of dollars.

ECMC's website has been offline since the virus was discovered Sunday; however, officials said it should be back up later Wednesday night.

That's one step in the long and complex restoration process.

Thursday, patient data should be accessible again, the hospital says. This includes things like electronic medical records. That patient data won't be fully integrated until Saturday, when doctors, nurses and others will be able to input new records.

Also Saturday, the email system should be back up and running.

I.T. professionals have been re-imaging about 6,000 desktop computers that had to be wiped clean as a result of the virus. The process of getting them back and ready to go is already underway, and that work continues.

A hospital spokesperson said ECMC should be able to release more information about the cause of the virus in the coming days. The FBI and State Police are among the agencies assisting ECMC with the investigation.

The local FBI declined to provide any information on the ongoing ECMC investigation.

A backup is now being used to restore the old computer system. Experts say having such a backup is key to not having to pay a ransom when hackers attack.