OAKLAND — Moments after thick, black smoke filled an eastbound bore of the Caldecott Tunnel on Friday morning, hundreds of motorists abandoned their cars and fled the tunnel, many clutching children’s hands and carrying dogs.

“I was in my car, when all of a sudden, one or two people walked past me, then three or four, then five, then six,” said San Ramon resident Kevin Watkins, whose car was stuck in the bore. “I got out and asked what was going on, and someone said we were asked to evacuate the tunnel.

“It was kind of scary. It took everybody aback.”

Seven children and one adult were taken to hospitals to be treated for smoke inhalation Friday in the aftermath of a blaze that broke out at 9:51 a.m., when a 1988 Acura Legend was engulfed in flames about 500 yards from the Orinda tunnel exit. The blaze, which fire officials think started in the car’s engine, was contained about 10:30 a.m., though thick smoke remained in the eastbound bore for the rest of the morning.

Moraga-Orinda Fire Department Battalion Chief Sean Perkins said fire crews contacted the Caldecott control center and requested that exhaust fans be redirected to blow smoke toward Orinda to keep visibility clear for motorists exiting the tunnel on the other end. The fans were installed after an explosive 1982 fire in the tunnel that killed seven.

However, fire crews had to enter the tunnel from the Orinda side through thick smoke, with very little visibility, Perkins said.

“Engine 45 crept along moving a couple miles per hour until they reached the car,” Perkins said.

MOFD firefighters, along with two Oakland engines from the other direction, extinguished the fire. The center bore was closed in case fire crews needed to access the affected tunnel through a passageway that connects both tunnels.

Watkins, 33, said he pulled up about 9:45 a.m. to the tunnel, which already was congested with the usual morning traffic. As he entered the tunnel, a California Highway Patrol officer pulled up with his lights on and moved everyone to the right side of the bore, effectively grinding traffic to a halt.

Soon after, Watkins said, every individual inside of the tunnel was asked to evacuate. Some pulled allergen masks from their car before leaving, or wrapped scarves around their faces to avoid breathing the smoky air.

Watkins grabbed his iPad and backpack, then hurried from the dark, smoky bore with an estimated 150 to 200 other motorists. The stranded commuters were asked to wait for instructions on the center divide for about 40 minutes, said Watkins, adding that officials asked the group if anyone was a nurse or an EMT.

“People were coughing a lot from the very beginning,” he said. “I wouldn’t be surprised to hear that people went to the hospital.”

Oakland Fire Battalion Chief Lisa Baker said seven children were taken to Children’s Hospital Oakland to be treated for smoke inhalation, and one adult was taken to Alta Bates. All hospitalizations were made as a precaution, she said, and no serious injuries were reported.

The 1982 fire in the westbound bore killed seven people after a drunken driver’s stalled car, a speeding bus and an overturned gasoline tanker combined to cause a superheated, toxic fire, one of the worst tunnel fires in U.S. history. Inadequate monitoring, lack of changeable message signs or signals at the entrance and inside, and lack of communication between tunnel personnel and motorists contributed to the severity of the fire, the National Transportation Safety Board later concluded.

Today, tankers carrying hazardous chemicals are prohibited from traveling through the tunnel for 22 hours a day, and emergency responders are equipped with more tools, such as cameras throughout each bore, to react to emergencies more quickly and efficiently.

Signs warn the 160,000 motorists who drive through the three bores each day to slow for accidents, and wiring has been added for cellphone communication.

MOFD and Oakland firefighters train a couple of times a year for Caldecott Tunnel fire response, Perkins said. Usually, they shut down a bore in the middle of the night for training.

About 11 a.m., the middle bore of the Caldecott Tunnel was switched to accommodate eastbound traffic, CHP Officer Ron Simmons said, and all lanes of traffic in both eastbound bores were open by noon. Officials said a hanging electrical wire that briefly closed one lane of the right bore was caused by the incident itself, and it was ruled out as the cause of the fire.

Staff writers Harry Harris and Matthias Gafni contributed to this story. Follow Erin Ivie at Twitter.com/erin_ivie.