Federal investigators are in Montana trying to figure out what caused an Amtrak train derailment that left at least three people dead and dozens more injured. Meg Oliver has the latest. Each weekday morning, "CBS Mornings” co-hosts Gayle King, Tony Dokoupil and Nate Burleson bring you the latest breaking news, smart conversation and in-depth feature reporting. "CBS Mornings" airs weekdays at 7 a.m. on CBS and 8 a.m. ET on CBSN. Subscribe to “CBS Mornings” on YouTube: https://www.youtube.com/CBSMornings Watch CBSN live: http://cbsn.ws/1PlLpZ7c​ Download the CBS News app: http://cbsn.ws/1Xb1WC8​ Follow "CBS Mornings" on Instagram: https://bit.ly/3A13OqA Like "CBS Mornings" on Facebook: https://bit.ly/3tpOx00 Follow "CBS Mornings" on Twitter: https://bit.ly/38QQp8B Subscribe to our newsletter: http://cbsn.ws/1RqHw7T​ Try Paramount+ free: https://bit.ly/2OiW1kZ For video licensing inquiries, contact: [email protected]