An American scientist working for a government agency has learnt the hard way that when the authorities say 'no chewing of gum or eating candy in subway stations', they mean it.

Stephanie Willett, a 45-year-old scientist for the Environmental Protection Agency, was eating a candy bar while riding the escalator into the Metro Centre junction in Washington, DC.

Metro Transit Police Officer Cherrall Curry-Hgler warned Willett to finish the candy before entering the station because eating or drinking in the Metro system is illegal.

Suspecting that Willett would not be obeying her order, she followed her.

Moments after she repeated her warning to Willet, Curry-Hagler searched, handcuffed and arrested her for chewing the last bite of her candy bar after she passed through the fare gates, reports said.

Willett was released from a police lockup after she paid a $10 fine, pending a hearing.

"We have been doing our best to crack down on people who are consuming food and beverages in our stations because we get so many complaints about it," said Lisa Farbstein, a Metro spokeswoman.

Willett said she was being unfairly punished because she told the officer while still swallowing the candy bar: "Why don't you go and take care of some real crime?" "Next thing I knew," Willett said, "she pushed me into the cement wall, called for backup and put handcuffs on me."

"It was humiliating," said Willett, who is to appear in court in October. "It was a complete waste of taxpayer's money and the officers' time as well as mine."