The interstate is the main artery that connects New York, Providence and Boston in the region. The accident site is near the state's two large casinos, Mohegan Sun and Foxwoods Resort Casino.

Kevin Nursick, a spokesman for Connecticut's Department of Transportation, said its crews would assess damage to the road only after the police complete their investigation.

"It's hard to tell at this point what repairs might be needed," he said. "We don't want to be under foot trying to assess roadway conditions while they're still trying to investigate this tragic accident."

All lanes in both directions remained closed as the afternoon rush hour picked up. Some or all lanes could remain closed through midnight or even into early Saturday depending on the length of the investigation and severity of the roadway damage, Nursick said.

Authorities also shut Interstate 395 from exit 77 south to I-95 and a portion of Route 1. The state police urged drivers to avoid the area if possible. East Lyme High School canceled all after-school activities, including a play and a football game, because of traffic.

Phyllis Martino of Wallingford was en route to a job interview at Foxwoods when she saw the accident.

She told The Day of New London that the tanker truck was driving north, tailgating a minivan and swerving in and out of traffic until it hit a guardrail, lost control and crossed the median into oncoming traffic.

The tanker truck is owned by Northeast Carriers LLC, which had a satisfactory rating, the highest possible, from the Federal Motor Carrier Safety Administration.

A message seeking comment was left with Northeast Carriers.