The Texas professor who allegedly told authorities that 30 vials of plague were missing when he knew they had been destroyed has been arrested, officials say.

Dr Thomas Butler, 61, headed a research programme at Texas Tech University Health Center in Lubbock to develop antibiotics to cure the disease.

He is reportedly charged with making false statements to the Federal Bureau of Investigation (FBI).

We have determined that there is no danger whatsoever Lupe Gonzalez, FBI agent

The FBI was called in as part of a major security alert after university officials discovered that between 30 and 35 vials were unaccounted for.

Officials had said they were unsure if the vials had been stolen or merely misplaced.

President informed

The White House was informed, and experts from the Center for Disease Control were called in immediately to join the investigation, together with dozens of FBI agents.

But on Wednesday the FBI accounted for the missing vials.

The FBI did not provide any other details, saying only that an investigation was still under way.

But Lupe Gonzalez, the FBI special agent in charge of the investigation has been quick to calm the public.

"We have determined that there is no danger whatsoever," he said.

'Black Death'

Plague caused huge epidemics in the Middle Ages, notably the Black Death that wiped out up to a third of the population in Europe.

But nowadays it can be treated with antibiotics, provided it is caught in its early stages.

It is an infectious disease caused by a bacterium named Yersinia pestis.

People usually become infected after being bitten by a flea which lives on rats and carries the bug.

The typical sign of the most common form of human plague is a swollen and very tender lymph gland in the neck.

This is known as a bubo - hence the name bubonic plague.

Other symptoms include fever, chills, headache, and extreme exhaustion.

Plague can also take two other forms - pneumonic plague, when the bacteria are inhaled, and septicemic plague, which is a rare blood infection.