A helicopter struck overhead power lines and crashed onto a barge on the Mississippi River near West Alton, Missouri, around 11 a.m. local time on Thursday, killing both people aboard, according to the St. Charles County Police Department. The impact ignited a fire and prompted the U.S. Coast Guard to halt vessel traffic between mile markers 199 and 201, a stretch just north of St. Louis that handles agricultural and industrial shipments. The crash also forced the temporary closure of the Lewis and Clark Bridge linking Missouri and Illinois; authorities did not provide an estimate for its reopening. Investigators from the National Transportation Safety Board and the Federal Aviation Administration have been dispatched to determine the cause of the accident. No injuries were reported on the barge or among first responders.