Cleanup of last week’s Mississippi River oil spill continues, as a handful of ships have been allowed to make their way downriver. Meanwhile, more questions have been raised about the safety record of a Louisiana towing company that owned a tugboat involved in last Wednesday’s accident.

Almost 800 cleanup workers used containment booms, vacuum skimmers and other equipment over the weekend to scrub oil-coated riverbanks. Around 10 ships and barges have been stranded on the river due to the oil spill. According to the Times-Picayune, fifty vessels were allowed to move inside the spill zone Saturday, up from only four Friday. Two cleaning stations have been set up for ships leaving the spill zone, one at New Orleans and the other near the mouth of the river. As of Saturday afternoon, three ships had been allowed to pass into the Gulf of Mexico, and another was able to leave the zone’s northern end. Another 10 ships were cleared to leave the zone once they are cleaned.

So far, the final cost for the Mississippi River oil spill has not been determined. However, the cleanup costs for similar tanker spills averages around $23 million, according to the Government Accountability Office.

The Mississippi River oil spill occurred when a 600-foot tanker and a barge loaded with fuel collided. The spill occurred about 1:30 a.m. central time Wednesday near the Crescent City Connection, a pair of New Orleans bridges. The barge split in half, spilling more than 419,000 gallons of tar-like oil into the river. The barge’s owner, American Commercial Lines, immediately took responsibility for the oil spill.

The ill-fated barge was being pushed by the tugboat the Mel Oliver. Last week, the US Coast Guard determined that no one on the Mel Oliver had the proper licensing for piloting a tugboat. The operator on the Mel Oliver at the time of the collision had only an apprentice mate’s license, and no one else on the barge had a license. To legally pilot a tugboat, an operator is required to have a master’s license.

According to the New Orleans Times-Picayune, on July 12, another DRD tugboat, the Ruby E., sank four miles up river from last weeks oil spill after colliding with another ship. Unlike the accident that spawned the Mississippi River oil spill, all of the crew on the Ruby E. was properly licensed, and the tugboat was not towing any cargo when it sank. Three crewmembers were on board the Ruby E. when it went down, but all were rescued without injury. Investigators have not released the names of the crew on either vessel, so it is not known if any crewmembers had been working on both ships at the time of either accident