At least 19 people were killed while 11 others were injured after a passenger bus plunged into a ravine in Balochistan's Zhob district on Sunday morning, officials said.

The bus, which was carrying more than 30 passengers, was travelling from Islamabad to Quetta.

Television footage showed rescue workers assisting bloodied passengers, while in another scene, the wreckage could be seen.

Sherani Assistant Commissioner Mehtab Shah told Dawn.com that the incident occurred near Dhana Sar. He said that the bus plunged into the ravine while speeding, killing 19 passengers and injuring 11 others.

Rescue teams rushed to the scene soon after receiving information, Shah said, adding that the bodies had been taken to the hospital where the process to identify them was under way.

Medical superintendent of Civil Hospital Zhob, Dr Noorul Haq, said that the injured being brought to the facility were in critical condition. He also said that the death toll was expected to rise.

Meanwhile, Balochistan Chief Minister Mir Abdul Qudoos Bizenjo expressed grief over the lives lost in the incident. He also offered his sincere condolences to the victims' families.

He ordered an emergency be declared in Civil Hospital Zhob to ensure treatment for the injured.

Later, Prime Minister Shehbaz Sharif also expressed deep grief and sorrow over the lives lost. The premier directed the authorities concerned to provide immediate and medical aid to the injured, a Radio Pakistan report said.

Last month, 22 people were killed, including nine members of a family, when a passenger van fell into a ravine near Qila Saifullah district of northern Balochistan. The van, carrying 23 passengers and en route to Zhob from Loralai, fell into the 200-foot-deep ravine when it reached Akhtarzai area.

Hafiz Muhammad Qasim Kakar, the deputy commissioner of Qila Saifullah, said the driver was speeding and broke through a protective wall at a bend in the road, falling hundreds of feet into the ravine.