San Antonio police have arrested a man who they said was selling counterfeit prescription drugs online.

Javier Francisco Soriano is charged with delivering and offering dangerous drugs.

He was arrested after a joint investigation with San Antonio police's Financial Crimes Unit, Homeland Security and the Food and Drug Administration.

Investigators say he was selling knock-off male enhancement drugs online.

Undercover officers purchased some and had them tested in a lab.

"At one point, the Viagra he was selling online claimed to be 100 milligrams but through the tests, they discovered it was 20 milligrams," said San Antonio police spokesman Officer Roger Zuniga.

Police confiscated more than 700 pills.

Soriano's bond is set at $10,000.