MANILA, Philippines—The National Bureau of Investigation will invite for questioning the owner of a house in Bulacan it believes was used by the Alvin Flores robbery gang as a hideout.

Bureau agents, along with policemen, seized rifles, grenades, ammunition and other "tools of the trade," including fake Police and Bomb Squad uniforms, bullet-proof vests, a bolt cutter and a sledge hammer, during a raid on the house on Friday.

The house is located in Rocka Village in the town of Plaridel.

No one was in the house when the government agents arrived.

According to Roel Bolivar, head of the NBI Reaction, Arrest and Interdiction Division, they will invite Arlene Miron, the owner of the house, to shed light on the matter.

"Among other things, we want to know from her who rented the house... and from that we will assess the information and hopefully we'll be able to establish possible leads vital to our investigation," he told the Inquirer. He added that according to information the NBI gathered, the gang rented the house as a temporary hideout three weeks ago.

Asked if Miron was considered a suspect, Bolivar said that "as of now, we're after the occupants of the house who were the subjects of warrants of arrest."

Bolivar added that apart from the arms cache, they also found pictures of a woman "who looked exactly the same" as Flores' sister, Merlinda, as shown on the PNP Wanted poster.

Merlinda also has a standing warrant of arrest for robbery. She is also considered a key player in the criminal group's operation, Bolivar added.

"Those pictures that we found there could be an indication that she (Merlinda) stayed at that house," Bolivar said, adding that the authorities also found documents, including the birth certificate of a child. "It's possible that it belongs to her child."

Bolivar said the NBI was planning to file charges against Merlinda for the arms cache.

Flores, allegedly one of the country's most notorious criminals and leader of the gang believed to be behind the daring robbery at the Greenbelt 5 mall in Makati two weeks ago, was gunned down along with three of his men during what the NBI has described as a shootout between the alleged robbers and lawmen in Compostela, Cebu, last Oct. 29.

The Flores Gang has been implicated in 14 robberies this year and 27 in 2008 in Metro Manila and nearby areas.