BOGOTA, Colombia -- A mystery illness has overwhelmed a small town in northern Colombia as scores of teenage girls have been hospitalized with symptoms that parents fear could be an adverse reaction to a popular vaccine against cervical cancer.

Authorities say they still don't know what caused more than 200 girls in El Carmen de Bolivar to come down with symptoms ranging from fainting to numbness in the hands and headaches. Some have hinted that the town of 95,000 near Colombia's Caribbean coast could be experiencing a rare case of mass hysteria.

Parents are on edge, however, because all the girls, ranging in ages from 9 to 16, were injected in recent months with the vaccine Gardasil. On Wednesday, residents marched peacefully to demand a thorough investigation.

Get Breaking News Delivered to Your Inbox

Francisco Vega, the town's mayor and a trained physician, told The Associated Press that illnesses first appeared at the end of May and have been steadily increasing since. Over the weekend, 120 girls were rushed to hospitals, collapsing the town's limited medical facilities. None of their symptoms were life-threatening and all have since been released, he said.

Echoing the assurances of national health and toxicology experts, who have traveled to the town to collect blood samples and investigate possible environmental hazards, he said there's no evidence the vaccine, which has undergone extensive testing and regulation globally, is to blame.

Meanwhile, Health Minister Alejandro Gaviria is criticizing hyped coverage by the media for stirring panic, saying concerns about their vaccine, which has been applied to 2.9 million women in Colombia, are baseless.

"On one side we have the weight of scientific evidence and on the other are opinions and moral prejudices," he told W Radio on Wednesday, adding the cervical cancer claims the lives of more than 3,000 women every year in Colombia.

Veronica Trulin, head of communications in Latin America for Merck, said all lots of the vaccine, including the ones sent to Colombia, meet all required quality and safety standards.

"We don't comment on speculation about our products," she said in an email.