Updated

PLEASANT VALLEY, N.Y. -- The wife of Robert F. Kennedy Jr. has been charged with driving under the influence of drugs one month after her license was suspended following her guilty plea to driving while impaired by alcohol, state police said Tuesday.

Mary Richardson Kennedy, 50, initially was pulled over Saturday morning for speeding on the Taconic State Parkway in Dutchess County, in the Hudson Valley, state police told The Associated Press. They did not specify how fast her Volvo was going, the results of her sobriety test or what drugs she allegedly had taken.

Kennedy told the trooper who stopped her after she was observed driving 82 mph that she was headed to a yoga class, The Journal News reported. She was driving alone.

After her arrest, she was taken to the state police barracks in Millbrook and examined by a drug-recognition expert, who determined she was under the influence of a prescription medication, the newspaper said. It did not identify the drug.

Kennedy is scheduled to appear in Pleasant Valley Town Court on Thursday.

There is no phone listing for the Kennedy home in Bedford, a New York City suburb. Robert Kennedy has reportedly filed for divorce and police records indicate Mary Kennedy lives in nearby Mount Kisco, but a phone number for her could not immediately be found.

Mary Kennedy's lawyer, Kerry Lawrence, did not immediately respond to a voice mail left by the AP at his office early Tuesday, but he told The Journal News, "We look forward to defending the charges against Miss Richardson Kennedy."

Kennedy was first arrested May 15 on a charge of driving while intoxicated after a police officer reported seeing her drive her car over a curb near the Bedford home. Her only passenger was a dog. Police said she had a blood-alcohol level of 0.11 percent; the legal limit is 0.08 percent.

She avoided jail time by pleading guilty to a lesser charge, admitting in court last month that her driving ability was impaired during the incident.

The judge fined Kennedy $500, suspended her driver's license for 90 days and ordered her to attend two drunken-driving programs.

Kennedy had a conditional license that allowed her to drive under certain circumstances, The Journal News reported.

Lawrence told the newspaper that his client was heading to the Omega Institute in Rhinebeck, an accredited educational center, and that she was allowed to drive there under the terms of her conditional license. The conditional license was issued Aug. 12, the day after her license suspension went into effect.

Mary Kennedy's first arrest came three days after Robert Kennedy filed a matrimonial action with the Westchester County clerk's office, naming his wife as defendant. Several news reports said he had filed for divorce, and most such filings are divorce suits, but the papers are sealed and both Kennedys have refused to comment.

Robert Kennedy, a prominent environmental lawyer, is the son of Sen. Robert F. Kennedy and nephew of President John F. Kennedy, both assassinated in the 1960s. Mary Kennedy is his second wife. They have four children.

Bedford police said in May that they had responded to the Kennedy home twice in the week before Mary Kennedy's arrest but no crimes had been committed.