WASHINGTON (MCT) — A federal strike force charged 91 doctors, nurses and other licensed medical professionals across the country in connection with phony bills totaling nearly $430 million — the latest in a series of busts by the Obama administration to attack rising government losses to health care fraud.

In Los Angeles, 18 people were charged, including three doctors and a licensed physical therapist, in schemes alleged to have cost the government $53.8 million. Four of them were accused of billing the government $49.2 million for ambulance rides in Southern California that were not medically necessary.