Bay Bridge officials said Friday they are reviewing plans to open a natural tunnel underneath the bridge, which has become the subject of a federal investigation into safety issues.

The Bay Bridge is a popular tourist attraction in the Bay Area, with tourists swarming to the span for its iconic bridges and restaurants and museums.

The Federal Aviation Administration said Friday that it has ordered the FAA to conduct an independent investigation of the Bay Bridge to determine whether it was unsafe.

The agency also said it was conducting an investigation into whether the Bay Tunnel, which is under the span, has enough security to protect passengers.