Afghan security officials said Wednesday that the death toll from a Taliban attack in Kabul a day earlier had jumped to 64, with an additional 347 people injured, amid signs that militants could be acquiring more powerful explosives.

The attack Tuesday on an Afghan intelligence training compound now ranks as one of the deadliest strikes on Kabul since the Taliban insurgency began in 2001.

The scale of the carnage also raised concerns that the Taliban is now turning to the military-grade explosives used by Iraqi insurgents against U.S. forces a decade ago — capable of toppling buildings and killing hundreds of people at a time.

As Afghan security officials continue to investigate the incident, what is known so far points to a powerful and coordinated strike just a week after the Taliban announced plans to step up attacks during a spring offensive.

The attack began when a truck packed with explosives detonated next to a compound used to train security guards for government leaders. The force of the explosion leveled part of the compound, creating a shock wave that shattered windows and cracked building facades up to two miles away.

“One thing is clear, that the amount of explosives in this attack seems to have been hundreds of [pounds] given the destruction it caused,” said Fauzia Zaki, a former general and member of the Afghan parliament.

For much of the insurgency, the Taliban generally relied on relatively low-yield explosive devices, often delivered by suicide bombers or in vehicles. While such strikes have killed thousands of people in Afghanistan over the past 14 years, the impact of each attack was usually confined to a relatively small area.

But over the past six months, security officials in Kabul have witnessed a disturbing new trend. Increasingly, they say, the Taliban is packing explosives into massive truck bombs capable of delivering a far deadlier punch.

Last August , a massive truck bomb detonated in eastern Kabul, crumbling several residential buildings and killing 15 people.

Then, in January, in an attack described as one of the largest bombs ever to be detonated in Afghanistan, a huge explosion tore through two compounds that housed U.S. embassy contractors and U.N. personnel, killing one person.

When the bomb detonated Tuesday in Kabul, the force of the explosion caused a ceiling to collapse in a classroom where elite intelligence officers were being trained. One security official, who asked not to be identified because of the ongoing investigation, said members of that unit accounted for about half of the people killed.

The Afghan Interior Ministry, however, said civilians made up the bulk of the fatalities.

On the floor of the Afghan parliament on Wednesday, several lawmakers blasted President Ashraf Ghani for failing to keep the public safe.

The magnitude of the explosion is also raising questions about where the Taliban is acquiring materials to make such destructive devices. Many Afghans blame Pakistan, which is likely to further complicate Ghani’s efforts to work with Pakistani leaders to try to bring the Taliban into peace talks.