Coalition officials were not sure if the column, which was attacked Wednesday afternoon, represented a counterattack on the Umm Qasr area or if it was a tactical retreat from Basra. 

Coalition troops decided not to split hairs, British pool journalist Bill Neely reported. 

"Quite simply the allies weren't taking any chances," he said. "This is war. It was a large target, a large column, and the decision was made to attack it." 

Basra has been pounded heavily by British artillery in recent days, Neely said. Some of the same guns were used to attack the column as it headed south. 

In Umm Qasr Wednesday, British Marines found a large cache of hand grenades and rocket-propelled grenades stored in a school. (Arms cache found) 

British forces uncovered the munitions after moving through this southern port city in a "rather robust fashion, arresting people, doing house-to-house searches," he said. 

Saddam Hussein has long been accused of hiding weapons in civilian buildings, such as mosques, hospitals and schools. 

Neely said this was the first evidence he had seen to confirm those accusations as British forces have established control of the region. 

The military uniforms found in the school, he said, may be an indication that the estimated 120 Iraqi troops there discarded their military clothes and "melted away into the civilian population." 

In a similar incident Tuesday, U.S. forces found a crate of machine guns at a hospital "used as a fortress,"Victoria Clarke, chief Pentagon spokeswoman, said.