FILE - In this July 22, 2003, file photo, nurses evacuate a patient after a fire broke out on the third floor of the 434-bed the formerly named Queen of Angels-Hollywood Presbyterian Medical Center, with visibly blackened windows, in the Hollywood section of Los Angeles. The FBI says Wednesday, Feb. 17, 2016, it is investigating a computer network extortion plot at the Los Angeles hospital. In the attacks known as "ransomware," hackers lock up an institution's computer network and demand payment to reopen them. FBI spokeswoman Laura Eimiller said Wednesday that the agency is investigating such a plot at the Hollywood Presbyterian Medical Center. (AP Photo/Nick Ut, File)

The computer systems at a Hollywood-area hospital started acting up on Feb. 5. Quickly, administrative officials realized the system had been subject to a ransomware attack, and critical computer files were locked through powerful encryption.

Hackers demanded a ransom for the decryption key.

Although the IT department was investigating, and the hospital was cooperating with law enforcement officials, no solution could be found. Necessary computer functions like CT scans remained down, and patients had to be moved to other area hospitals as hospital staff relied on fax machines to get patient information to doctors and nurses, reports said.

Yesterday, Allen Stefanek, the Hollywood Presbyterian Medical Center CEO, released a statement acknowledging the hospital paid the ransom amount requested of 40 Bitcoins or approximately $17,000—probably the first well-known cases of a ransomware attack on a hospital. The statement refuted original accounts that the ransom demanded was more than $3 million—or 9,000 Bitcoins.

“The quickest and most efficient way to restore our systems and administrative functions was to pay the ransom and obtain the decryption key,” Stefanek said.

But, according to experts, ransomware attacks aren’t always released to the public, and they might be much more common than previously thought.

“Unfortunately, a lot of companies don't tell anybody if they had fallen victim to ransomware, and especially if they have paid the criminals,” Adam Kujawa, the head of a San Jose-based anti-malware company, told the AP.

According to a 2014 report, the number of attacks each month rose from 100,000 in January to 600,000 in December of 2013.

Bitcoins are an online form of currency that are notoriously hard to track. They are quickly becoming the preferred currency for hackers, or other online criminals, like those involved with the Silk Road—a dark net, black market for illegal drugs shut down by the FBI in 2013.

Regarding this case, the FBI said an investigation of the attack is currently underway, but would not release any other information.

The Associated Press contributed to this reporting.