MANILA, Philippines--One of the three supposed operators of the backhoe found at the crime scene in Maguindanao province is now under police custody, a police official said on Monday.

But Chief Superintendent Felicisimo Khu, Task Force Alpha commander, declined to name the operator of the backhoe pending official investigation.

Police are still looking for two more operators of the backhoe that was reportedly used to dig a shallow grave to hastily bury the 57 victims in the killings.

Khu said that initial investigation revealed that the backhoe went up the crime scene in November 18 and went down again on 22nd, purportedly to dig the grave.

The backhoe then reportedly went up again on November 23, the day of the killings, Khu said.

“[We have one] in our custody [but] he was not the one who operated the backhoe [at the crime scene]. He was just one of the three operators of the backhoe,” Khu said.

“I have directed CIDG-12 (Criminal Investigation and Detection Group) to get any valuable statement from him that will have relevance to the mass murder,” he added.

Earlier, the CIDG named one backhoe operator as a certain Hanid Delayudin.

The victims were mostly part of the convoy of supporters and relatives tasked to file the certificate of candidacy of gubernatorial aspirant Esmael “Toto” Mangudadatu and journalists assigned to cover the filing.

Mangudadatu will challenge political rival Andal Sr., the Ampatuan clan patriarch for the gubernatorial seat.

Datu Unsay Mayor Andal Ampatuan Jr. on Thursday surrendered to authorities after being tagged as mastermind of the killing.