Recently unsealed Drug Enforcement Agency warrants reveal that San Diego Chargers team doctor Dr. David Chao is a focus of their investigation, KGTV in San Diego reports.

According to the documents, the DEA discovered that Dr. Chao wrote over 150 prescriptions for controlled substances to himself.

"My training and experience lead me to suspect that David Chao has possibly self-prescribed or possibly used prescriptions to obtain controlled substances for office dispensing to patients, violating at least one of these regulations, which as a registrant he is required to obey," a DEA agent wrote in the warrant.

The DEA's decision to investigate was prompted by the May 24 arrest of then-Chargers safety Kevin Ellison, who was in possession of 100 Vicodin tablets without a prescription.

After Ellison's arrest, his attorney claimed that Ellison was in possession of the pain-killers to treat a knee operation. Ellison underwent three procedures on his knees during his four years at USC, but started 9 of 13 games as a rookie and by all accounts, had no surgical procedures on his knee this off-season, and was a full participant in the Chargers' off-season workout program.

Ellison's attorney has also denied that the investigation into the Chargers' medical staffs was not related to Ellison's arrest.

The Chargers waived Ellison in June, and he was claimed, released, and re-signed by the Seattle Seahawks, whose head coach, Pete Carroll, recruited and coached Ellison at USC.