The unnamed worker has been accused of attacking Iranian asylum seeker Reza Barati, who died from injuries while being transferred to hospital.
Media reports suggested staff at the centre were aware who had struck Barati during riots amid simmering tensions at the Australia-run centre two weeks ago.
No one has been arrested in connection with the death, but a PNG autopsy found Barati died after repeatedly being struck on the head with a piece of timber.
A Salvation Army spokesman said the organisation had investigated claims one of its employees was responsible for Barati's death and "found absolutely no evidence that it occurred".
"The PNG authorities are investigating this and they will determine what has gone on," he added.
"I think everyone needs to respect that and take a step back while they conduct the investigation.
"From our perspective, it would be inappropriate for us to comment any further as we could potentially prejudice any investigation currently underway."