OAKLAND, Calif. -- Caltrans officials said today that the new eastern span of the Bay Bridge is safe despite an FBI investigation into allegations of misconduct involving substandard welding procedures during construction of the new span.

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Caltrans District 4 Director Bijan Sartipi, who oversees the Bay Area, said, "We want to assure the public that all work is being performed to the highest standards."

Caltrans Director Will Kempton, who oversees the agency's operations statewide, said in a letter to the Oakland Tribune that was shared with other reporters, "Your readers can be assured that a safe bridge is being built."

The letter was written in response to a Tribune article saying that welders claim the Eastern span is riddled with defective welds

Kempton told the Tribune, "The article could lead your readers to believe the bridge is unsafe and I want to provide assurances that this is not the case."

Kempton said quality control and quality inspection processes regulate the welding process before, during and after the work to verify the welds are safe.

Kempton said, "Over 300,000 pages exist that clearly show the welds on the Bay Bridge have been inspected to the highest of standards. Improper welds are caught and corrected."

In a brief statement today, the FBI said it's looking into complaints which "consistently allege a pattern of substandard welds affecting a number of pilings intended to support the new Eastern span."

The FBI said its investigation is based on a telephone call to its Bay Area Public Corruption Hotline.

According to the FBI, no one has been charged in connection with the investigation at this point.

The Office of the Inspector General of the U.S. Department of Labor and the U.S. Department of Transportation are working on the investigation with the FBI.

Project lead contractor Kiewet Corp. said in a statement that its welding on the Bay Bridge "is performed in compliance with stringent Caltrans specifications as well as the American Welding Society Codes."

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Kiewet, which is based in Omaha and has its West Coast office in Concord, said, "Critical welds are performed by certified, experienced union welders that are approved by Caltrans."

Weld testing and inspections are carried out by Caltrans, Kiewet's quality department and an outside third party inspector, Kiewet said.

Kiewet company officials said, "These state-of-the-art measures are employed daily on every critical weld to ensure that our work on the Bay Bridge project is in full compliance with all contract specifications."

Sartipi said, "We're satisfied the welding is being done properly."

He said the FBI has contacted Caltrans as part of its investigation and he promised, "We will cooperate fully."