PORTLAND – Alcohol was not a factor in the crash of an oil tanker into the Casco Bay Bridge connecting Portland and South Portland, the Coast Guard said Tuesday.

It may take several weeks to determine the cause of Monday’s accident, which damaged the bridge’s fender system but did not cause injury or environmental pollution, said Mike McCarthy, a spokesman for the Coast Guard.

Investigators administered alcohol tests to captain Nicolas Garanganis, as well as the second mate and helmsman of the 31,700-ton Hawk, McCarthy said.

Also tested were local docking master Arthur Fournier and his assistant. All the tests came back negative.

In September 1996, when another oil tanker hit the old Million Dollar Bridge over Casco Bay, investigators failed to conduct an alcohol test on James Mooney, the docking master who had given the wrong directions to the crew.

Mooney had not been drinking, but the lapse in protocol led to censure by the National Transportation Safety Board after 180,000 gallons of oil spilled into Portland Harbor.

Testing for substance use now is mandated by federal law.

On Tuesday, the Coast Guard divers conducted a visual scan of the tanker’s hull. No exterior cracks were found, McCarthy said.

Divers next will inspect the bridge’s damaged fender system, said Bill Johnson of the Maine Department of Transportation.

Authorities credited the fenders with minimizing the impact of the oil tanker on the bridge, which sustained no structural damage.

But state officials estimated that damage to the fenders will cost hundreds of thousands of dollars to repair.

Jim Lawrence, a spokesman for Hawksleigh Trading Corp., which owns the ship, said he doesn’t know what caused the accident. The Athens, Greece-based firm will cooperate in the Coast Guard’s investigation, he said.