Quetta, Pakistan — Pakistani insurgents opened fire on Tuesday at a passenger train in the country’s restive southwestern Balochistan province, wounding the driver and prompting security guards aboard the train to fire back, officials said. After the attack, the train came to a stop in a remote area in the Bolan district and the fate of the passengers was not immediately clear.

The separatist Balochistan Liberation Army, which has been waging a yearslong insurgency in Pakistan, claimed responsibility for the attack. Officials at Pakistan Railways said the Jafar Express train was carrying an estimated 500 passengers, including women and children. 

A Baloch Liberation Army source told CBS News’ Sami Yousafzai that the group had killed six security personnel as it seized control of the train, but the group’s claim could not be verified.

The train was traveling from the provincial capital of Quetta to the northern city of Peshawar when it came under attack, government spokesman Shahid Rind said, adding that enforcements were heading to Bolan to respond to the situation. He had no further details.

He later said that ambulances were dispatched but that access to the site was not easy due to the mountainous and rugged terrain. He described the attack as “an act of terrorism” and said Bolan hospitals were put on an emergency level.

Trains in Balochistan typically have security personnel on board as separatists have previously carried out deadly attacks on trains and security forces in the region.

A Pakistani security official in Quetta told CBS News’ Yousafzai that the BLA militants had destroyed the tracks before the train arrived, forcing it to stop in the mountainous area, possibly inside a tunnel. The official said the attack, which left the train driver injured, “created significant challenges for security forces responding to the situation.” 

“We have not yet established contact with the attackers or passengers, but it’s most likely a hostage situation,” the official said, adding that security forces were preparing for a major operations.

Authorities did not immediately confirm any casualty figures, but an emergency situation was declared at nearby hospitals.

In November, the Balochistan Liberation Army carried out a suicide bombing at a train station in Quetta that killed 26 people, including security personnel, railway staff and passengers. The group has been designated as a terrorist organization for years by both the Pakistani and U.S. governments.

Oil- and mineral-rich Balochistan is Pakistan’s largest, but also its least populated province. It’s a hub for the country’s ethnic Baloch minority whose members say they face discrimination and exploitation by the central government.