BALTIMORE -- The WBAL TV 11 News I-Team has learned that Baltimore city faces a multimillion-dollar bill from the federal government to resolve a dispute over hundreds of ambulance calls over several years.

The dispute over $4 million was raised by a federal audit of Medicare billing.

Auditors claimed that in some cases, the city billed Medicare for the more expensive advanced life support in ambulance transports when it should have billed for basic life support.

The city is contesting the claim and the $4 million bill.

A spokesman for the mayor's office said the city has traditionally billed Medicare at the higher amounts because its medic units are certified at the advanced life support level. The spokesman said there is no indication of any malicious wrongdoing in the dispute.

The city has moved billing for ambulance runs out of the fire department to a private contractor.