Canadian man Nicolai Boutnine and Joseph Dean, an American, were among six suspects arrested when police raided a call-centre in the central city of Mandaue on Monday, the Philippine police criminal investigation group said.

Criminal charges were filed against the suspects following the police operation in response to a complaint from the pharmaceutical giant Pfizer that owns the erectile dysfunction drug's patent, said police spokesman Don de Dios.

"We are coordinating with the US Immigration and Customs Enforcement to secure some of the evidence needed for their prosecution," Senior Inspector de Dios told AFP.

He said the call-centre firm, 724Care Inc., used cloud computing technology provided by US online search giant Google to store sales data virtually.

This prevented local police from recovering sales receipts and related documents or the drugs themselves, whose location remains unknown.

He said they would need the US authorities' help in retrieving the data from the owner of the server that hosts the 724care.net account.

De Dios said the suspects, who also included four Filipinos, were charged for fraud and selling counterfeit drugs, both of which carry jail terms of up to 10 years.

Under these laws the suspects have the option to post bail, but de Dios said he was unaware if they had done so and if the court had ordered their temporary liberty.

Court officials in Mandaue were unavailable for comment on Saturday.