Initial reports said Mancao had been released from the custody of the FBI after he posted a bail bond of $575,000.
Mancao, who is based in Pembroke Pines in Florida, had been taken into custody by federal authorities as a "material witness."
The former police colonel was reportedly sought by the FBI as a possible witness against his former colleague Michael Ray Aquino, who is charged by the US government with espionage.
Philippine honorary Consul to Florida Lito Macatangay confirmed that Mancao was allowed to leave Miami Federal Detention Center in Florida.
The Department of Foreign Affairs (DFA), however, could not verify the report saying Manila had yet to receive information from the Philippine Embassy in Washington on Mancao’s reported release.
"We can’t confirm the report. We’re still awaiting the embassy report," DFA spokesman Gilberto Asuque said.
Macatangay earlier informed the Philippine embassy that he received a telephone call last April 14 from Mancao informing him that he voluntarily turned himself in to FBI officials in Miami, the day after he was sought by federal agents at his home.
Mancao and Aquino had served in the defunct Presidential Anti-Organized Crime Task Force (PAOCTF) then headed by former Philippine National Police (PNP) chief, now Sen. Panfilo Lacson.
Both were tagged as the prime suspects in the killing of publicist Salvador "Bubby" Dacer and his driver Emmanuel Corbito in November 2000.
Before they could be charged in Manila in July 2001, both fled to the United States. — Pia Lee-Brago