An armed gang of teen-agers who stole $81,470 from a cruise ship's casino in Port Everglades two weeks ago went for a six-hour pleasure trip aboard the ship before robbing their host, police said on Saturday.

It was an inside job, investigators said after the arrest on Saturday of three of the four people suspected in the Jan. 14 robbery of the cruise ship Discovery I.

The gang was led by a security guard who worked for the ship's casino operator, Broward Sheriff's Office spokesman Al Gordon said. They planned the robbery for a week and planted weapons on board before they struck, he said.

Sheriff's Office detectives, along with Metro-Dade police, arrested Jacques Edward Dubois, 19, of Opa-locka, who had worked in the ship's casino as a security guard on several occasions; Soraya Audain, 20, of Miami, who is thought to have driven the getaway car; and a 15-year-old boy.

A fourth suspect, Alvin Eugene Burke, 16, of Miami, remains at large, Gordon said.

Police recovered weapons, $37,000 of the stolen cash, and the clothing, masks and gloves worn during the robbery, Gordon said. He declined to say where the arrests were made.

Burke and the 15-year-old bought $59 tickets for the Saturday night dinner cruise and boarded the ship with the rest of the passengers, and Dubois boarded through a crew entrance using his security-guard identification, detectives said.

The three mingled with passengers during the six-hour cruise. "(They were) just taking a cruise, waiting for it to get over," Gordon said.

They hid in the casino air-conditioning maintenance room and waited for passengers to disembark and employees to begin counting money, Gordon said.

About 2 a.m., while nine ship employees were in the casino tallying the night's receipts, a masked man carrying a shotgun entered and ordered them to lie face down on the floor.

After gathering up the money, the bandit ordered the employees into a storage room, which he locked and tied shut.

After disembarking, the robbers left the port in a car in which Audain had been waiting, Gordon said.

Dubois was charged with 10 counts of armed kidnapping and one count of armed robbery, and Audain was charged with one count of armed robbery. Both are being held without bail in the Broward County Jail. The 15-year-old was released into the custody of his attorney, said Gordon, who said he did not know what charges were filed against the youth.

The arrests were made four days after detectives received an anonymous tip on the Crime Stoppers hot line, which led police to Burke, who Gordon said was later linked to Dubois.

The day before the tip came in, Discovery Cruises Inc. announced a $5,000 reward for information leading to the arrest and conviction of the robbers, and newspapers published composite drawings of the suspects.

"Discovery is thrilled with the speed with which the Broward Sheriff's Office has apprehended the criminals and solved the case," said Barbara Rubin, a spokeswoman for Discovery Cruises Inc. "We feel good that they have gotten these people off the streets."

"It is the first time we can remember that a casino was knocked off inside Broward County," Gordon said. "It was a very high priority case."

SUSPECTS IN HEIST

Officers have arrested Jacques Edward Dubois, 19, of Opa-locka, a former ship security guard; and Soraya Audain, 20, of Miami; and a 15-year-old boy in the Jan. 14 robbery of the cruise ship Discovery I. A fourth suspect, Alvin Eugene Burke, 16, of Miami, remains at large.