PORTLAND — Drug agents have arrested five people in connection with a crackdown on the illegal sale of oxycodone pills, a prescription painkiller that is popular among illicit drug users.

Agents with the Maine Drug Enforcement Agency and the Portland Police Crime Suppression Unit raided hotel rooms on Riverside Street and stopped two cars in the culmination of an investigation that started two months ago.

Police seized 201 30-mg pills and $21,000.

MDEA Supervisor Kevin Cashman said a surge in demand for the pills corresponds with changes in the manufacture of the medicine that make more recent shipments harder to abuse.

Willie Johnson, 29, of Dorchester, Mass., Barry Wright, 38, of Louisville, Ky., and Rahdahl Harvey, 34, of Hyde Park, Mass., were charged with aggravated drug trafficking because they have prior drug convictions and they are being held on $50,000 bail at Cumberland County Jail.

Sean Evans, 23, of Westbrook and Audrey Chambers, 22, of Buxton were charged with trafficking in oxycodone.