More than 40 students from a military school whose convoy was ambushed by Taliban militants in Pakistan’s lawless tribal region are still being held captive, a school official said June 3, contradicting the military’s claim the entire group had been freed.

A string of buses ferrying students and staff out of the restive territory was ambushed on Monday night, but the chief military spokesman said all those seized were rescued hours later. The spokesman did not immediately return calls on Wednesday.

The ambush was one example of increasing militant attacks in recent weeks in South and North Waziristan–along the Afghan border–in what authorities say is an attempt to distract the military from its offensive against the Taliban in the nearby Swat Valley region.

Javed Alam, the director of studies at Cadet College Razmak, told The Associated Press on June 3 that 42 students and three teachers from the school had not been rescued, and some had been allowed to call home.

"Two or three of the abducted students were allowed by their captors to talk to their parents," Alam said. "During their brief phone conversation, they said that they were being treated well, they were being given food, but we have no idea exactly where they are being held."

No ransom or other demands were made, and the captors did not identify themselves, he said.

The details of Monday’s raid remained murky, with different officials giving differing accounts–some claiming that up to 500 people had been taken.

Alam said 113 students and five teachers were abducted in the initial ambush, and all but one busload of people was recovered when the army challenged the kidnappers at a checkpoint. Shots were fired, but no one was injured in the rescue, the military has said.

The ambush also came as thousands of residents fled North and South Waziristan because they expect the military to launch a new phase in the campaign against militants. The military says it is responding to militant attacks there, but has not started a broader campaign.

The area is a longtime stronghold of the Taliban and al-Qaida, and U.S. and other officials say the militants are using it as a base to plan and launch attacks on international forces in Afghanistan.

Richard Holbrooke, U.S. President Barack Obama’s special envoy to Pakistan and Afghanistan, was due in the Pakistani capital of Islamabad on Wednesday for talks on the offensive against the Taliban and the refugee crisis it has triggered.

Some 3 million people have fled the Swat region in the past weeks, with hundreds of thousands living in sweltering camps just south of the conflict zone and the rest renting or staying with family or friends.