The Broward County school district’s emergency handbook states that students should be evacuated from portable classrooms into permanent school buildings during a tornado warning, contrary to what school officials said on Wednesday.

The Sun-Sentinel quoted district spokeswoman Sisty Walsh as saying on Wednesday that the district’s procedure allowed principals to decide whether to leave children in portables, even when a tornado has been sighted in the air or located on radar.

Judith Hunt, the district’s safety director, said on Thursday that she might have misspoken or been misunderstood when she briefed Walsh. Hunt also told Walsh on Wednesday that the evacuation procedure was based on state regulations. But Hunt said on Thursday that a further inquiry showed the district’s procedure was actually drawn from informal advice on a poster issued by the state.

The district’s actual regulation states: “Students assigned to portable or temporary classrooms should be escorted to their assigned area within the main building during a tornado warning.”

But, in practice, several situations occur in which students are not or cannot be evacuated, Hunt said on Thursday.

The most common instance occurs when the main school building is so crowded that there is no practical place to safely house a large number of children. Auditoriums, cafeterias and gymnasiums have large roofs that may collapse if a tornado passes by.

Students may also be left in portables when a tornado is already close to the school. It is safer to keep children inside the portables, away from the windows and under desks, rather than to risk taking them outside when a twister is approaching, Hunt said.

Some schools are completely made up of portables, such as Eagle Point Elementary in Sunrise, and have no permanent buildings available. Some all-portable annexes are blocks away from the main building campus, such as Northside Elementary in Fort Lauderdale.

Schools Superintendent Frank Petruzielo referred all questions about the district’s policy to Hunt.

Principals frequently pull children out of portables simply when they know a strong rainstorm is imminent, Hunt said.

Parents called the Sun-Sentinel on Wednesday concerned that children were left in portables during severe weather. Terri Rivera and other parents were somewhat relieved when the procedures were clarified on Thursday.

But Rivera said her child attends Pine Lakes Elementary in Pembroke Pines, one of the most crowded schools in the district. She remained concerned that there was probably no place for her children to take cover in the main school building.

“Maybe they could put them in hallways. I don’t know if that’s possible. What we need are new schools.”

The safety of leaving children in portables is debated by local, state and national officials.

Portables are sturdier than most people might think because the state requires they be able to withstand 120-plus mph hurricane winds, said Ed Hubert, structural engineer for the state Department of Education.

And most of Broward’s 1,760 portable classrooms are secured with metal straps that tie the frame to concrete footings, Associate Superintendent Ray de la Feuilliez said.

But Hubert said the stresses of a tornado are completely different, and more destructive, than a hurricane. Tornadic winds of 70 to 200 mph suck at the top of a building and the circular winds attack a structure from different angles, Hubert said.

Hubert said students would not be considered safe during a tornado unless they were not only inside a permanent building, but in its center with the most structural support. Outside walls of permanent buildings can collapse under a tornado’s buffeting.

No structure is immune to the direct hit of a tornado and a twister can do significant damage to a portable classroom even without directly striking the structure, said Brian Smith, disaster specialist with National Weather Service in Omaha, Neb.

In damage he surveyed after a tornado in the Tampa Bay area in 1992, Smith saw mobile homes whose frames were tied down to the concrete. The frames were still there, but the rest of the structures were gone.

Dennis Decker, Smith’s counterpart in Melbourne, echoed those concerns, but he noted that tornadoes in South Florida are generally weaker than the ones that strike the Omaha area.