A construction worker was injured late Thursday night on southbound Interstate 405 near State Route 167 while installing electrical conduit in the median for the I-405 widening project.

The cause of the accident was under investigation.

Washington State Patrol closed all lanes of southbound I-405 at SR 167 while fire and aid crews assessed the construction worker’s condition and transported him to the hospital. All lanes were reopened just after Friday midnight.

The work is part of the I-405/I-5 to SR 169 Stage 1 Widening project.

The project adds a lane in each direction on I-405 between I-5 and SR 167 and a lane on southbound SR 167 between I-405 and Southwest 41st Street.