KABUL — Sweeping arrests have been made by desperate Afghan authorities trying to end the alleged serial poisoning of schoolgirls, but some doctors now suspect psychological stress could be behind the "attacks", officials said Tuesday.

Sixteen suspects have been detained in the past four days over the mysterious illnesses -- usually including mass fainting episodes -- that have struck scores of schoolgirls in northern Takhar province almost daily for the past two weeks.

Among those held are a Pakistani woman working in a clinic and a Taliban insurgent leader, provincial spokesman Mostafa Rasuli told AFP. All have denied any involvement, and no proof of poisoning has been found, he said.

No girls have died from the alleged attacks -- which are also reported periodically from other parts of Afghanistan -- and most are released soon after being rushed to hospital, officials confirm.

But the authorities have been under pressure from frightened families to "do something" about the alleged attacks, which have affected hundreds of girls, sources in Takhar say.

As AFP reported last week, an international expert in the field is convinced that the incidents are classic examples of mass psychogenic illness, or mass hysteria, rather than poisoning.

Some doctors in the area now share this belief, an education ministry spokesman, Abdul Saboor Ghufrani, said Tuesday -- a day on which 60 schoolgirls in two separate schools were affected.

"There have been a number of suspected poisoning cases of schoolgirls in Takhar province recently, but initial investigation by health and security teams in the area have failed to detect traces of any poison," Ghufrani told AFP.

"In some cases doctors in the area have reported they suspect a psychological cause behind these incidents, but we cannot yet definitely rule out the possibility of a deliberate attempt by some group to sicken our students.

"Some suspects have been detained in recent days and police are interrogating them. We have to wait for the outcome of the investigation."

Local officials regularly accuse Taliban insurgents, who banned schooling for girls while in power from 1996 to 2001, of poisoning school wells or using "gas" or "toxic powder" against the girls.

But with no physical cause established, Robert Bartholomew, a sociologist and author specialising in the field, told AFP the poisoning scares had "all the earmarks of mass psychogenic illness, also known as mass hysteria".

Bartholomew said he had collected more than 600 cases of mass hysteria in schools dating back to 1566 in Europe, "and the Afghan episode certainly fits the pattern".

The tell-tale signs include the fact that most victims are girls, the absence of a toxic agent, the rapid onset of and recovery from symptoms, and anxiety generated by a wartime backdrop, he said.

He noted there was a history of similar cases in combat zones, listing examples from the Palestinian territories in 1983 to Soviet Georgia in 1989 and Kosovo in 1990.

While the Taliban, with their history of brutal treatment of women, are an easy target for the government and its Western backers and the alleged cruel attacks win headlines worldwide, it is the girls who suffer from a lack of transparency over the "attacks".

The Afghanistan Times daily made the point in an editorial quoting the AFP report last week, saying children could be kept from school out of fear and "keeping a child away from education is the worst form of ignorance and offence".

Women have made great strides in Afghanistan since the Taliban were toppled in a US-led invasion after the 9/11 attacks on New York and Washington, but fear is widespread that those gains could be lost as NATO troops withdraw by the end of 2014.