AUSTIN (KXAN) — Multiple agencies, including the National Transportation Safety Board, are investigating the Interstate 35 crash that killed five people in north Austin. The NTSB said it expects to be at the scene for at least a week investigating what happened in the crash. "I want to once again give my condolences to the families who lost loved ones and the friends who lost one loved ones and those who were injured in this tragic crash. It is the mission of the NTSB to ensure the safety of the traveling public," said Alvin Brown, the Vice Chairman of the NTSB during a press briefing Sunday afternoon. Around 11:20 p.m. Thursday, southbound I-35 was reduced to one lane in a north Austin construction zone at Howard and Parmer Lane. Overnight lane closures are a common occurrence in construction zones, but that night, authorities said at least 18 vehicles including several semi-trucks were involved in a crash. According to an arrest affidavit, witnesses told investigators “all traffic was nearly stopped" when the crash happened. The crash killed five people, including an infant and a child, and closed the highway for nearly 14 hours. The stretch of interstate, between Howard Lane and Parmer Lane, is within the construction zone of the I-35 Capital Express North Project. It's an area that currently has lanes blocked in by concrete barriers to protect construction workers. Truck driver in fatal I-35 crash allegedly under influence of drugs, affidavit says "The design of the work zone in the roadway, that is a definite focus of this comprehensive investigation," said Kenny Bragg, senior highway safety investigator. As part of the I-35 Capital Express North Project, the Texas Department of Transportation is constructing an HOV lane in both directions of I-35 between State Highway 45 North and U.S. Highway 290 East. KXAN Traffic Anchor Erica Brennes asked TxDOT about the crash and if construction zone changes would be considered. Though they didn't answer that question directly, TxDOT told KXAN that drivers should continue to use caution in work zones, that pavement can be uneven, traffic patterns can and do change. The NTSB investigation will include a final report that may include recommendations for changes to the construction zone and protocol, but that could take up to two years to complete. Fatal I-35 crash: NTSB provides second update on its investigation "Our objective is to find out what happened and why it happened so that we can make recommendations to ensure that it doesn't happen again," said Bragg. The I-35 CapEx North project won't be done until 2029. The central portion is being done in phases, and it may not be done until 2033. The I-35 Capital Express South portion of the project is expected to last until 2028. Drivers should slow down and use extreme caution with I-35 through Austin under construction for for the better part of the next decade ...read more read less