Initial Pakistani Interior Ministry reports that five people survived the Airblue crash were wrong, said Imtiaz Elahi, chairman of the Capital Development Authority, which deals with emergencies and reports to the ministry.
"The situation at the site of the crash is heartbreaking," Elahi told The Associated Press. "It is a great tragedy, and I confirm it with pain that there are no survivors."
The U.S. Embassy says two American citizens were among the 152 people killed in a plane crash in the hills surrounding Pakistan's capital.
Embassy spokesman Richard Snelsire did not provide further details about the two Americans.
Local TV footage showed twisted metal wreckage hanging from trees and scattered across the ground on a bed of broken branches. Fire was visible and smoke rose from the scene as a helicopter hovered above. The army said it was sending special troops to aid the search.
"I'm seeing only body parts," Dawar Adnan, a rescue worker with the Pakistan Red Crescent, told the AP 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 search effort was hampered by muddy conditions and smoldering wreckage that authorities were having trouble extinguishing by helicopter, Adnan said.
The cause of the crash was not immediately clear, said Pervez George, a civil aviation official. The plane left the southern city of Karachi at 7:45 a.m. for a two-hour scheduled flight to Islamabad and was trying to land during cloudy and rainy weather.
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 50 bodies from the wreckage, said Ramzan Sajid, spokesman for the Capital Development Authority.
"The plane was about to land at the Islamabad airport when it lost contact with the control tower, and later we learned that the plane had crashed," said George, adding the model was an Airbus 321 and the flight number was ED202.
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.
"We don't know who survived, who died, who is injured," said Zulfikar Ghazi, who was waiting to receive four relatives. "We are in shock."
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 crash.
Officials at first thought it was a small plane, but later revised that. George said 146 passengers were on the flight along with six crew members.
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 was no more than eight-years old, and it had no known technical issues, Ahmed said. The pilots did not send any emergency signals, he 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 321 jets. There were no casualties and damage was minimal, according to the U.S.-based Aviation Safety Network.
The Airbus 320 family of medium-range jets, which includes the 321 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.
Associated Press Aviation Writer Slobodan Lekic in Brussels, as well as AP Writers Ashraf Khan in Karachi and Zarar Khan in Islamabad contributed to this report.