HOUSTON (AP) — Houston Fire Department officials say more than 40 students have been taken to hospitals after being sickened by fumes possibly from tar work on nearby roofs.

Authorities responded to the Young Women's College Preparatory Academy in Houston late Thursday morning. The fire department says students were transported to hospitals, as a precaution, after complaining of nausea and headaches.

Officials initially believed the students were sickened by a possible gas leak. But CenterPoint Energy spokeswoman Alicia Dixon says the company determined the incident was not related to natural gas.

Authorities later determined the students were likely sickened by fumes from tar being used for roof repairs in the area.

The fire department cleared the scene by early Thursday afternoon and said no hazards were found.