A Los Angeles hospital has paid hackers a ransom of 40 bitcoins ($23,400) to regain control of their computer system after a cyber attack.

Doctors were forced to relay on paper records using their notoriously messy handwriting, after electronic communications between physicians and medical staff were crippled in a "malware attack" on February 5.

The attack locked them out of their systems by encrypting files for which only the hackers had the decryption key, Hollywood Presbyterian Medical Centre's president Allen Stefanek said.

Paying the ransom was the "quickest and most efficient way" of regaining access to the affected systems, Mr Stefanek said.

He said the 434-bed facility initially notified law enforcement and computer experts worked feverishly to restore system access and uncover the source.

Mr Stefanek said there was no evidence any patient or employee information was accessed and the hospital fully restored access to its electronic medical record system on February 15.

"Patient care has not been compromised in any way," Mr Stefanek said.

Although the cyber attack snarled the hospital's patient database, doctors managed to relay necessary medical records the old-fashioned way through phone lines and fax machines, said Dr Rangasamy Ramanathan, a neonatal-perinatal specialist affiliated with the hospital.

The origin of the computer network intrusion remains unknown.

The FBI and the Los Angeles Police Department are working to pinpoint the hacker or hackers responsible for the attack, FBI spokeswoman Laura Eimiller said.

Reuters