PORTLAND – A Portland teen-ager pleaded innocent Tuesday to manslaughter for allegedly being drunk when he drove his car off a bridge, killing three of his friends.

Michael O’Brien, 19, came to court in a wheelchair and was released on $10,000 bail in connection with the January accident, when his car plunged off the side of Tukey’s Bridge on Interstate 295 in Portland.

Prosecutors decided to charge O’Brien with manslaughter when tests showed he had a blood-alcohol level of 0.12 percent. O’Brien also was charged with three counts of aggravated operating under the influence.

The legal limit for people 21 and older is 0.08 percent. It is illegal for people under 21 to drive with any amount of alcohol in their blood.

Police say O’Brien was driving more than 100 mph at 2:30 a.m. Jan. 12 when he lost control of his car. The car fell off the bridge and landed upside down on a pedestrian path.

The accident killed Crystal Young, 18, and Jason Carr and Nathaniel MacConnell, both 19. The three were high school seniors in Portland.

Police are investigating whether the teen-agers had been drinking at a place called Horseshoes in Portland, which police have described as an unlicensed illegal bar.

A Portland lawyer said the owner of the property served a couple of beers to the teen-agers, but said Horseshoes is not an illegal bar.

Under the terms of O’Brien’s bail, he is not allowed to drive or use drugs or alcohol. And he has a court-imposed curfew from 6 p.m. to 6 a.m.