WASHINGTON (AP) — A top federal health official says a health worker diagnosed with Ebola has been unable to identify a breach in procedures that might have led to her infection.

Dr. Tom Frieden, head of the Centers for Disease Control and Prevention, says the Texas hospital worker had extensive contact with Thomas Eric Duncan before Duncan died Wednesday from Ebola.

Frieden says the worker has a low level of virus and is being monitored.

He says the diagnosis of the worker — who’s not identified — clearly shows that there was a breach of protocol.

Among the things CDC will investigate is removal of protective gear, because removing gear incorrectly can lead to a contamination.

The investigation will look at dialysis and intubation — procedures with the potential for spreading infectious material.