Updated at 11:37 a.m. Eastern.
A passenger jet crashed into the hills overlooking Pakistan's capital amid poor weather Wednesday, killing all 152 people on board and blazing a path of devastation strewn with body parts and twisted metal wreckage.
It was the worst plane crash ever in Pakistan, and rescue workers battled fires and muddy conditions as they searched in vain to find survivors on the densely wooded hillside where the flight went down.
"The situation at the site of the crash is heartbreaking," said Imtiaz Elahi, chairman of the Capital Development Authority, which deals with emergencies and reports to the Interior Ministry. "It is a great tragedy, and I confirm it with pain that there are no survivors."
The dead included two U.S. citizens, said the U.S. Embassy in Islamabad without providing further details.
The crash left twisted metal wreckage hanging from trees and scattered across the ground on a bed of broken branches. Clouds of dense gray smoke rose up from the burning wreckage as a helicopter hovered above.
"I'm seeing only body parts," Dawar Adnan, a rescue worker with the Pakistan Red Crescent, said by telephone from the crash site. "This is a very horrible scene. We have scanned almost all the area, but there is no chance of any survivors."
The cause of the crash was not immediately clear, but Defense Minister Chaudhry Ahmed Mukhtar said the government does not suspect terrorism.
The plane left the southern city of Karachi at 7:45 a.m. for a two-hour Airblue flight to Islamabad and was trying to land during cloudy and rainy weather, said Pervez George, a civil aviation official.
CBS News correspondent Mark Phillips reports that Pakistan is now in the monsoon season, when heavy rains and dense cloud move up from the Indian Ocean -- and the weather at the scene of the crash was terrible. Some other flights have reportedly been cancelled over the past few days.
Airblue is a private service based in Karachi, Pakistan's largest city, and Wednesday's flight was believed to be carrying mostly Pakistanis.
Rescue workers scouring the heavily forested hills recovered nearly 80 bodies from the wreckage, said Pakistan's National Disaster Management Authority in a statement.
The flight was carrying 146 passengers and six crew members, said George. The aircraft was an Airbus A321, and the flight number was ED202, he said.
Interior Minister Rehman Malik initially said five people survived the crash and were rescued, but those reports turned out to be wrong.
A senior official with Pakistan's Civil Aviation Authority told CBS News' Farhan Bokhari the government had ordered an urgent investigation into the plane's "unusual flight pattern" in the moments before the crash.
The crash site covered a large area on both sides of the hills, including a section behind Faisal Mosque, one of Islamabad's most prominent landmarks, and not far from the Daman-e-Koh resort.
At the Islamabad airport, hundreds of friends and relatives of those on board the flight swarmed ticket counters desperately seeking information. A large cluster of people also surrounded a passenger list posted near the Airblue ticket counter.
"My life has come to a virtual end," sobbed Sobia Khan, a woman in her 20s who was surrounded by a group of friends. She said her husband was on the flight.
Shakeel Malik, a young engineer whose sister-in-law was on the ill-fated flight tearfully told CBS News his wife had to be sedated she was so distraught. "We have no hope of her survival," said Malik.
Saqlain Altaf told Pakistan's ARY news channel he was on a family outing in the hills when he saw the plane looking unsteady in the air. "The plane had lost balance, and then we saw it going down," he said, adding he heard the thunderous crash.
The Pakistan Airline Pilot Association said the plane appeared to have strayed off course, possibly because of the poor weather.
Raheel Ahmed, a spokesman for the airline, said an investigation would be launched into the cause of the crash. The plane had no known technical issues, and the pilots did not send any emergency signals, Ahmed said.
Airbus said it would provide technical assistance to Pakistani authorities responsible for the investigation. The aircraft was initially delivered in 2000, and was leased to Airblue in January 2006. It accumulated about 34,000 flight hours during some 13,500 flights, it said.
The last major plane crash in Pakistan was in July 2006 when a Fokker F-27 twin-engine aircraft operated by Pakistan International Airlines slammed into a wheat field on the outskirts of the central Pakistani city of Multan, killing all 45 people on board.
Airblue flies within Pakistan as well as internationally to the United Arab Emirates, Oman and the United Kingdom.
The only previous recorded accident for Airblue, a carrier that began flying in 2004, was a tail-strike in May 2008 at Quetta airport by one of the airline's Airbus A321 jets. There were no casualties and damage was minimal, according to the U.S.-based Aviation Safety Network.
The Airbus A320 family of medium-range jets, which includes the A321 model that crashed Wednesday, is one of the most popular in the world, with about 4,000 jets delivered since deliveries began in 1988.
Twenty-one of the aircraft have been lost in accidents since then, according to the Aviation Safety Network's database. The deadliest was a 2007 crash at landing in Sao Paolo by Brazil's TAM airline, in which all 187 people on board perished, along with 12 others on the ground.