It began as a drill, and the more people became involved, the more believable it got. More than 100 public safety volunteers gathered Saturday for a mass casualty drill at the little bridge in Oak Bluffs. There were sirens, fake blood on the ground and children screaming in apparent pain.

Beach road from Oak Bluffs to Edgartown was closed to all traffic. Onlookers watched in amazement as the scene came alive in an instant after a call was heard on the radio. A Coast Guard helicopter hovered overhead. There were calls that people were on the water and under the water.

The call first came over the communications center dispatch. Annie Nichols, assisted by Linda Cook, made the announcement over the radio at 11:10 a.m.

"A taxi van, heading from Oak Bluffs into Edgartown on Beach Road, swerves to avoid a small child, hits the child and goes through the railing and off the bridge on the pond side. Unknown number of people in the cab, unknown number of people at the bridge railing at the time of the accident."

Within a minute, an Oak Bluffs police cruiser came speeding along the road. Police officer Jim Morse rushed from his cruiser and surveyed the crash scene near the little bridge. Children were lying on the ground. A vehicle appeared deep in the rushing waters of the channel under the bridge.

"Stay where you are," said the police officer. Meanwhile, the first of several ambulances and other emergency vehicles began to arrive. A Coast Guard helicopter appeared overhead, its noise deafening. EMTs wearing blue latex gloves carried boxes of medical supplies.

A dispatcher from the communications center came on the air again to report the crash as a mass casualty incident, which means other towns are paged. Public safety officials swiftly responded from Edgartown, Oak Bluffs and Tisbury, as well as cruisers carrying state police. The harbor masters of both towns arrived by water. Edgartown Rescue and Dive Team made up of five divers and supporting crew, along with six divers from the Oak Bluffs fire department and their support crew, also rushed to the scene.

They took direction from Oak Bluffs assistant fire chief Pete Forend.

Divers went down and recovered the bodies of three youngsters in the practice vehicle, Dodge Omni that was placed underwater earlier. Divers carrying the youths were met at the shoreline by emergency medical technicians and other firemen. Two victims were recovered from the water in Sengekontacket Pond. The divers were told a third person was still missing.

The U.S. Coast Guard hovered over Sengekontacket Pond. A crewman aboard the helicopter spotted the sixth passenger of the car submerged in the pond.

Using radio communication between the helicopter and police, the divers were sent to the right spot to dive and recover the last of the missing people, a drowned victim.

Meanwhile three ambulances were loaded with injured children and adults, all bystanders.

The helicopter overhead kicked dust and spray into the air. An EMT, moving across the little bridge, remarked to his colleague that this drill was becoming a little too much like the real thing.

"I hope it never happens for real," said officer Morse.

Ten-year-old Jaime Lynn Billings, the youngest volunteer victim, was assisted towards an ambulance.

In less than an hour, the last of the ambulances was on its way toward the hospital, and the crash the scene was cleaned up.

Judy Amaral of Oak Bluffs put away the quart-size container of fake blood.

Saturday at 4 p.m., many of the emergency medical crews involved from Island towns showed up for a cookout at the Nelson Amaral fire station in Oak Bluffs. Like students, forever in school, the meeting was an opportunity for fun and fellowship, but also for debriefing after the morning's exercise.

In the 23 years he has been a member of the Oak Bluffs fire department, Captain David Billings said he has never seen a more realistic drill than what occurred earlier in the day. "More than 15 years ago," he said, "we didn't have drills."

Deputy fire chief Ralph Norton stood before the gathering and said: "I want to thank all of you for work." The drill was a great success, he said.

John Rose, a captain of the ambulance in Oak Bluffs, co-organized the day with the help of Joan Condlin of the Edgartown fire department, also an emergency medical technician. "We have never have dealt with so many different agencies," he said.

"We need this exercise," Mr. Rose said. "Ninety-five per cent of the Island EMTs are volunteers. It is difficult to have a drill like this. All of them have real jobs on the side. It is so valuable to have this kind of event. This is where you find out where the problems lie."

Mr. Rose told those gathered at the fire station that he had high praise for their efforts. He said EMTs received praise from hospital personnel handling the incoming wounded. He said that the word from hospital personnel was that patient care was superb.

"I had lots of issues," said Mike Gilman of Aquinnah, one of the 12 volunteer victims, who spent most of the drill face down on rocks near the water. By the time of the cookout, Mr. Gilman had washed most of the stage blood from his face. Though he never said a word during the drill, he described his conditions. " I had a ruptured spleen, I had superficial wounds, was in shock and was vomiting."

Mr. Norton said: "I really have to thank the public for coping with the inconvenience of of the road being closed. It may have been an inconvenience for the day. But understand that emergency personnel volunteering are inconvenienced every day of their lives."

Fire chief Dennis Alley said: "As far as I am concerned, this went really well. I have nothing but praise for John Rose and Joan Condlin. The amount of hours they put into the effort, over 100 hours, versus the amount of time of the drill, less than an hour, is really something. They worked so hard."