PORTLAND – A Portland teen-ager consumed alcohol at an unlicensed home business before he flipped his car over a guardrail on Interstate 295, killing his three passengers and seriously injuring himself, police said.

Michael O’Brien, 19, had been at the establishment known as Horseshoes before he lost control of his car at the approach to Tukey’s Bridge early Sunday, according to investigators.

Later that day, state liquor enforcement agents and Portland police seized cases of beer and prepackaged mixed drinks from the establishment, said Stephen McCausland, spokesman for the state Department of Public Safety.

McCausland said the owner of Horseshoes, John Donovan Sr. of Portland, was cooperating with investigators and had not been charged with any crime.

As of this year, furnishing alcohol to a minor can be a felony offense, punishable by up to five years in prison if it leads to a death. The legal drinking age in Maine is 21.

O’Brien’s three passengers, Jason Carr, Nathaniel MacConnell and Crystal Young, all died at the scene. The three, all seniors at high schools in Portland, also are believed to have been drinking at Horseshoes, according to investigators.

On Monday, friends, relatives and classmates of the dead teen-agers gathered in small groups at the spot where the three died. Bouquets and mementos formed a makeshift shrine in memory of the lives cut short.

“I’m in shock now,” said Nickie Sweetsir, a classmate of Young at Portland High School. “After the shock is over, we’ll just have to learn from this. It should be a lesson – everyday you have to appreciate everyone around you.”

Maine State Police Trooper George Loder said two carloads of teens were headed from Horseshoes to Falmouth, possibly to a house.

O’Brien, driving one of the cars, passed the other car at a high rate of speed and glanced against a concrete barrier. His Ford Taurus careened diagonally across the two lanes and hit a 6-inch stone curb with enough force to flip it through the air and send it over the guardrail and the steep embankment, landing upside down on a jogging path.

Loder said that when he arrived O’Brien was conscious and told him that he had been drinking.

Portland High School Principal Michael Johnson said it was too soon after the deaths to drum home the message that drinking and driving are a deadly combination.

“It’s a very difficult thing during the mourning process. The kids don’t want to hear it. They’ve heard it a thousand times. No, they’ve heard it a million times. … I’m sure there will at some point be a discussion at Portland High School about this issue, but not yet.”