WASHINGTON — NASA and Boeing are investigating a recent mishap at the Michoud Assembly Facility that damaged a portion of a liquid oxygen tank being developed for the Space Launch System.

Kim Henry, a spokesperson for NASA’s Marshall Space Flight Center, said May 10 that NASA and Boeing, the prime contractor for the SLS core stage, have established independent investigation teams to review an incident at Michoud one week earlier involving the rear dome of a liquid oxygen qualification tank. The mishap was first reported by NASA Watch.

The agency didn’t provide additional details about the incident, which took place in the Vertical Assembly Center at Michoud, used to weld large components of the SLS. The Vertical Assembly Center was shut down when the incident took place, Henry said. “NASA is evaluating next steps to safely resume operations.”

The damage was limited to the one dome section of the tank, which was not yet welded to the rest of the tank. “Assessments are ongoing to determine the extent of the damage,” she said.

Henry said that the incident was classified as a “Type B” mishap. Such a mishap, according to NASA documents, covers incidents that cause between $500,000 and $2 million in damage. No one was injured, she said.

The liquid oxygen tank involved in the incident was a qualification model, intended for testing, and not flight hardware. Henry said it wasn’t immediately clear how long the investigation would take.

The accident comes as other factors, some outside of NASA’s control, have threatened to delay development of the SLS. A tornado struck Michoud in February, damaging some buildings used for SLS and Orion work there. Agency officials estimated in March the repairs would delay work by two to three months.

Last month, NASA acknowledged that SLS, along with the Orion spacecraft and accompanying ground systems, would not be ready for launch in November 2018 as previously planned. In a response to a U.S. Government Accountability Office report, NASA said was now considering 2019 dates for the first SLS launch, known as Exploration Mission (EM) 1.

The schedule for that launch may also depend on a decision to put a crew on EM-1, which is currently planned to fly without astronauts on board. NASA officials said last month that a report studying the feasibility of placing a crew on EM-1 has been completed and briefed to agency leadership and the White House, but no decision has been announced yet.