By Rebecca Conway and Qasim Nauman
ISLAMABAD (Reuters) - Pakistani officials on Saturday promised a full investigation into the crash of a domestic flight that killed 127 people, saying they were examining all possibilities, from a technical fault to the age of the Boeing 737.
Grieving relatives claiming the remains of loved ones at a hospital expressed grief and anger over the crash in a storm as the plane approached Islamabad on a flight from Karachi, Pakistan's commercial hub.
Armed police kept media out of the Institute of Medical Sciences in the capital where the remains were stored.
With wreckage scattered over a square km of wheat fields, officials said there were no survivors.
At a press conference on Saturday, Nadeem Khan Yousafzai, director-general of Pakistan's Civil Air Authority, said the plane was locked into the instrument landing system, an approach system that provides precision guidance for aircraft, when it suddenly dropped from 2,900 feet to 2,000 feet.
"It just went down, into a dive," he said. "Then contact was lost and the blip disappeared from the radar."
"What happened in this period, that has to be investigated. Was there a downdraft, was there an engine failure?"
The Boeing 737-200 was more than 27 years old, according to AviationSafety.net.
Prime Minister Yusuf Raza Gilani, speaking outside the hospital earlier, said: "Until investigations are completed, we cannot jump to any conclusions."
Interior Minister Rehman Malik said the owner of Bhoja Air, Farooq Bhoja, had been barred from leaving the country to ensure his cooperation with the investigation. "Action will be taken, and will be seen to have been taken, I promise you," he said.
Bhoja Air started flights in 1993 but suspended operations eight years later because of financial problems. It resumed domestic flights only last month.
The plane's "black box", which records flight data, was recovered last night, rescue authorities said.
Bhoja officials were not immediately available for comment.
Many of the relatives gathered at the hospital had flown up from Karachi on Saturday morning for the task of identifying victims. Women and men sobbed openly and pushed reporters away.
"My brothers are gone! My brothers are gone!" wailed Mohammad Shahzad, slumping to the ground by the hospital entrance.
One brother had been identified, he said, the other remained missing. Both had been on a day-long business trip linked to the transport company run by the three siblings.
"We don't know what to tell the kids, we don't know what to tell my mother," Shahzad said. "They keep calling. I told them there was an accident and we don't know anything yet."
Ayesha Ishaque pressed her face against a light brown wooden coffin labeled "Body 140". Her brother, Mohammad Saud Ishaque, had been returning home from studies in Karachi.
"Why has God done this to my brother," she wailed.
Some gurneys with body parts in bags were taken inside. Also visible were clear plastic containers with bone fragments with labels like "bone from foot", "bone from arm" and "rib".
Three men from the national database agency were taking a cigarette break from identifying the bodies from fingerprints.
"We've identified at least 73 bodies so far, and at least 25 will have to be sent for DNA testing because their hands and digits could not be read," said one man, clearly exhausted, his latex gloves and blue overalls covered with blood stains.
A coffin periodically passed through the crowd with a piece of paper on top bearing the victim's name and identification number. Bystanders threw rose petals over the grim procession.
Security was intensified at Islamabad's Benazir Bhutto International Airport. Some women had their bags emptied and each item checked.
"I'm feeling okay to fly," said Mohammad Ehsan, 47, an engineer who had been scheduled to travel on the plane on the return flight to Karachi that it never made.
"I was in shock last night. When I saw the pain and grief the relatives were feeling I just couldn't think of taking a flight last night. I am grateful for being alive."
Afghan President Hamid Karzai expressed condolences to Pakistan over the crash.
In July 2010, an AirBlue jet slammed into the mountains ringing Islamabad on a foggy morning, killing all 152 aboard. Two other crashes that year killed 33 people.
Pakistan is rated a category 1 by the U.S. Federal Aviation Authority, which means it meets international standards for air safety.
(Additional reporting by Mahawish Rezvi; Writing by Chris Allbritton; Editing by Ron Popeski and Sanjeev Miglani)