Interstate 5 has completely reopened near Northgate after a fatal collision involving two semitrucks and two cars closed all southbound lanes for hours Tuesday morning, according to state traffic and law enforcement officials.

The collision occurred around 3:25 a.m., prompting officials to close all southbound lanes, according to the state Department of Transportation. Officials had reopened three right lanes by 8:42 a.m. and opened the remaining two lanes around 3:18 p.m.

The traffic backup was about six miles long around 7:30 a.m., according to the State Patrol.

The adult male driver of one of the semitrucks was killed in the collision, according to the State Patrol. Another man is in custody for investigation of vehicular homicide, Trooper Rick Johnson said.