Michael Sheehan, a spokesman for Celebrity Cruises, said an 83-year-old man, who was a U.S. citizen, had an apparent heart attack and died while the ship was at sea.

In addition, a 40-year-old woman who had "cancer issues" also died at sea while the ship was en route to Hawai'i from San Diego, Sheehan said.

Both of the passengers died Sunday.

Two other men aboard the Summit were referred to local medical facilities after it docked at Pier 10 at Aloha Tower, Sheehan said.

One of the men, 69, reported having numbness in his hands and feet, which was acute and progressive. The other man, 76, may have had a mini-stroke.

The two fatalities are not expected to interfere with the ship's schedule, Sheehan said.

The Bahamian-flagged Summit was scheduled to arrive at Pier 10 at 6:45 a.m. from San Diego.

It is expected to depart Honolulu for Lahaina, Maui, tonight, arrive in Kailua, Kona on Sunday and set sail for the return trip to San Diego later in the day, arriving back on the West Coast Nov. 9.

Scott Ishikawa, a spokesman for the state Department of Transportation, called the deaths "an unfortunate coincidence."

"Trips on cruise ships often appeal to the elderly, which was the case in one of the deaths," Ishikawa said.

"We understand that the second person who died was battling cancer, so it appears both deaths were due to natural causes and there were no suspicious circumstances," he said.

He said the bodies were turned over to the Honolulu Medical Examiner in case autopsies are deemed necessary.

Janice Okubo, spokeswoman for the state Department of Health, said deaths or sickness aboard cruise ships must be reported to the Centers for Disease Control if they involve contagious infections or diseases.

Both of the deaths aboard the Summit appear to have been the result of natural causes so the cruise line would not have been required to contact the CDC, Okubo said.

"We have a medical facility on board that would obviously assist anyone who is in ill health," Celebrity spokesman Sheehan said. "If you have an unfortunate situation where someone passes away, we have a guest care team that specifically assists the families and the people on board who may be traveling with the (deceased) person as well as the family on the shore side."

A death aboard the ship is reported to local authorities at the next port of call, Sheehan said.

The ship has a separate refrigerated facility that can accommodate as many as four bodies if necessary, Sheehan said.