NEW ORLEANS – The towing firm involved in last week’s Mississippi River oil spill also staffed a towboat that sank 11 days earlier with an improperly licensed and inexperienced pilot at the helm, raising questions about whether the economic and environmental disaster could have been prevented.

DRD Towing of Harvey operated vessels involved in the back-to-back accidents staffed with under-licensed crews, leading U.S. Coast Guard inspectors to board every boat in the company’s fleet to check credentials. They found no other violations when they searched 12 boats last Wednesday, the same day as the oil spill.

The Ruby E towboat was piloted by an apprentice mate when it collided with the Martin Challenger on July 13. Eleven days later, the Mel Oliver towboat was also piloted by an apprentice mate while pushing oil-filled barges when it collided with the chemical tank ship Tintomara. Both trips required pilots with master’s licenses.

Coast Guard spokesman Mike O’Berry confirmed the Ruby E’s inadequate credentials Monday, three days after saying that the crew was properly licensed.

The sinking of the Ruby E wasn’t the first demonstration of DRD Towing’s lax safety controls.

The firm failed a May safety audit and was already facing probation or revocation of membership from the American Waterways Organization, a national trade association for the tugboat, towboat and barge industry.

Lynn Muench, senior vice president of the organization, said each of its more than 350 members must pass comprehensive safety inspections every three years to demonstrate that its crews know and are following the Responsible Carrier Program, a thorough set of safety checks requiring certain skills and documentation of regular drills.

The organization now must decide whether to revoke DRD Towing’s membership or grant it probationary status, which would require annual safety audits.

A revoked membership in the trade group would come with staggering economic losses, as American Waterways Organization members can partner only with fellow members for transportation deals.