KABUL, Afghanistan — Police arrested the driver of a truck carrying three tons of explosives in what appeared to be an attempted suicide bombing in a section of the Afghan capital near a university for engineering, officials said Sunday.

The driver of the small cargo truck was approaching a security checkpoint near Kabul Polytechnic University just before midnight Saturday and ignored orders to stop, officials said.

Authorities said police at the checkpoint then fired at the truck, injuring the driver. They found 30 buckets filled with ammonium nitrate hidden beneath boxes of tomatoes inside the truck's cargo hold.

Kabul has been on high alert since a May suicide bombing near the German Embassy killed scores and injured several hundred. Investigators linked that attack to the Haqqani network, an offshoot of the Taliban.

"This could have been a massive suicide attack if it was not paralyzed," Mohamed Salem Almas, head of criminal investigations for the Kabul police, said of the Saturday night arrest.

In the same area of the city, investigators recently discovered a factory that they said was being used by the Taliban to make land mines and suicide vests.