Three years ago, an explosion at the Tesoro refinery in Anacortes killed seven people. Today, a federal investigation into the incident remains incomplete. And six members of Washington’s congressional delegation say that’s unacceptable.

In a letter this week, they again called on the U.S. Chemical Safety Board to finish the investigation and release the results so future such tragedies can be prevented.

The push is being led by Rep. Rick Larsen and Sen. Patty Murray.

In January, board Chairman Rafael Moure-Eraso wrote to the delegation to say the report had been delayed because the team working on it had been called away to other incidents multiple times.

He wrote that the board had not devoted a full-time investigative team to this one case since the month it happened.