Navy spokesman Capt. Geronimo Malabanan said Navy authorities ordered the probe based on a complaint from anonymous naval officers sent via e-mail.
"The Navy leadership is aware of this allegation and this is being looked into by Philippine Navy investigating bodies," he said. "This (complaint) was brought to our attention by (Paranaque Rep. Roilo) Golez, (chairman of the House committee on national defense) about two weeks ago."
Malabanan said the Navy will recommend the filing of criminal charges against Tan through its Office of Ethical Standards and Public Accountability, since Tan already reached the mandatory retirement age of 56 on March 10.
In several instances, the military recommended that the Office of the Ombudsman file criminal charges before civilian courts against retired military officers found to have committed irregularities while in the service, Malabanan added.
In a series of five e-mails to Golez, a certain Ernesto Gumising, believed to be a fictitious name, accused Tan of amassing millions of pesos from illegal transactions with several suppliers on behalf of the Navy.
"On March 10, this corrupt Navy officer will be retiring from the service and may be laughing to his heart’s content if we will allow him to retire with millions of pesos he amassed from illegal transactions of his own unit from the Navy’s budget," read one of the e-mails.
"Tan consolidated all direct fund support of the Philippine Fleet from second quarter to last quarter of CY 2004 in the guise of procuring centrally all the requirements of the eight forces and groups under him."
Gumising claimed Tan committed graft and corruption while he was concurrent Philippine Fleet commander last year after his predecessor, Rear Adm. Gilmer Batistel, had gone on leave.
"Worse, Tan withdrew or withheld the approved transactions during the time of Batistel to have more funds for his retirement," read one of the e-mails.
How he managed to take all these funds? He simply relieved all officers involved in the processing of procurement papers and even the finance/budget officers (and replaced them) with his own men.
"After he organized his team, all procurement papers were completed with the help of his own dealers and even bribed the accountant and auditor including their personnel."
Gumising said evidence against Tan and his accomplices can be compiled by making an inventory of supplies and materials that were supposed to have been delivered between the second quarter of last year and the present, and check the supply warehouses under the Philippine Fleet.
"These items are all consumables but were not delivered, meaning ghost deliveries," read one of the e-mails. "They have completed all the documents only up to the headquarters Philippine Fleet level, but not up to the forces and group levels."
Gumising named Tan’s alleged accomplices as his former procurement officer and aide-de-camp, Navy Lt. Ronald Landingin; a certain Commander Tejada, a comptroller; a certain Lieutenant Commander Costa, a logistics officer; Navy Capt. Edgar Azurin, a maintenance and repair officer; Ana Hallawany of Anwhel Trading; and a certain Mrs. Tecson.
"They knew that during audit, the inspectors only inspect the papers at the headquarters level," he said. "The supply officers of forces and groups were required to sign the requisition papers and issue slips and withdrawal slips and these papers amounted to millions."
In his fifth and last e-mail to Golez, Gumising threatened to disseminate the complaint to all Navy officers if Golez would not act on the matter. "The evidence is still there," read the e-mail. "Our empty bodegas will speak for the truth for the conversion/ghost deliveries that he has done."
Tan and the others accused by Gumising of irregularities could not be reached for comment.