Sarah Tessier Powell was last seen on Sept. 30, 2012 on board the Holland America cruise ship Veendam. (Halifax Regional Police)

Halifax Regional Police are asking for the public's help in locating a 70-year-old U.S. citizen who may have walked off a visiting cruise ship in the Maritimes.

Sarah Tessier Powell was last seen Sept. 30 on the Holland America cruise ship Veendam, as it sailed from Quebec City to Charlottetown.

The ship's next stops were scheduled in Charlottetown on Oct. 2, Sydney on Oct. 3 and Halifax on Oct. 4.

Police said they do not suspect foul play in Powell's disappearance and think she may have walked off the ship without being checked by security. It's not clear where Powell may have disembarked.

The Louisiana woman was travelling alone, said Halifax Regional Police Const. Pierre Bourdages.

"She was last seen by a crew member on board the ship, so it took time for them to realize she was not on board the ship any more," he said Tuesday.

"She left the ship without the crew's knowledge or security's knowledge on board."

Erik Elvejord, a spokesman for Holland America, said a ship-wide search was conducted for Powell.

"Per marine regulation and protocol, Transport Canada/Canadian Coast Guard (TC/CGG), United States Coast Guard, FBI, RCMP and local law enforcement authorities were contacted with all known information," he said in an emailed statement.

"An investigation is ongoing."

Powell is described as five feet six inches tall with a thin build and brown, shoulder-length hair. She speaks with a strong southern accent.

Halifax Regional Police said there is a concern for Powell's well-being because she requires medication and could become agitated without it.