COTABATO CITY, Philippines ? Barely a week after a Philippine Air Force Nomad plane crashed in an urban-poor neighborhood here that killed a general and eight others, a PAF fact-finding mission about to wrap up investigation is more likely to blame "mechanical failure" as the cause of the tragedy, a ranking military official said Tuesday.

"Mechanical failure is being eyed as the most probable cause of the crash after considering other angles," said Colonel Cris Tumanda, PAF tactical operations group commander for Central Mindanao.

Tumanda said the gathered pieces of debris from the crash site and testimonies of witnesses show a strong indication that mechanical failure caused the ill-fated aircraft to ascend abruptly.

Among those killed were Air Force Major General Mario Butch Lacson, commander of the 3rd Air Division based in Zamboanga City, seven soldiers and officers, and a civilian when the Nomad plane plunged into a subdivision here on January 28.

Rommel Quilantang, air traffic controller at the Cotabato Airport in Awang, Datu Odin Sinsuat, Maguindanao, said he was able to record the last communication he had with one of the pilots, First Lieutenant Angelica Valdez.

Quilantang said they heard "no unusual sound" from the ill-fated plane when Valdez was talking to them.

It was at 11:35 a.m. when Valdez radioed to say "thank you sir" in response to our "happy flying" send-off message, he said.

"But two minutes later, she radioed back requesting clearance to return to the airport," recalled Quilantang, saying, "Go ahead, proceed station, runway clear."

Sensing trouble, he asked the pilot if the sudden return to base was an emergency, and Valdez, in a calm and relaxed voice replied, "Yes, sir," said Quilantang, who confirmed the air mishap at exactly 11:38.a.m.

"There is a strong possibility the plane had a mechanical problem but we have yet to determine how it started because when it took off at Awang (airport), the plane was air worthy," Quilantang said.