Sen. Ted Kennedy, who has been undergoing treatment for a malignant brain tumor, was taken Friday to a hospital near his Cape Cod vacation home after suffering a mild seizure, according to his Senate office.

His office released a statement saying doctors believe the seizure was brought on by a "change in medication." The Democratic senator later returned home.

"Senator Kennedy experienced a mild seizure at home in Hyannis Port today and was taken to Cape Cod Hospital for examination," the statement said.

Sen. John Kerry, Kennedy's Massachusetts colleague, told FOX News earlier that he spoke with Kennedy and that he was in good spirits.

Kennedy arrived at the Cape Cod hospital "conscious and alert," according to a source close to the situation.

Barnstable police Sgt. Ben Baxter said a 911 call from the Kennedy compound in Hyannis Port came about 5 p.m. Friday.

Baxter said Kennedy was taken by ambulance to Cape Cod Hospital. He also said Kennedy was "alert and responsive" during the trip.

The source close to the situation said there was no indication doctors at Massachusetts General Hospital were mobilizing to receive Kennedy for treatment. Kennedy was flown to that hospital after suffering a seizure in May, an episode that led to Kennedy's brain cancer diagnosis.

After his seizure, Kennedy underwent surgery in June for a malignant brain tumor. After undergoing six weeks of chemotherapy and radiation treatment, he has been increasing his public activity.

FOX News' Carl Cameron and Major Garrett and The Associated Press contributed to this report.