(CNN) -- Four persons are missing after two boats collided shortly after midnight Saturday on the Mississippi River, said fire department officials in Burlington, Iowa.
One boat was carrying 11 people and the other only one, Battalion Chief Ken Morris of the Burlington Fire Department told CNN.
At least three persons were injured, and one of them was flown to Iowa City because of serious injuries, Morris said.
Authorities received a call at 2:30 a.m. ET Saturday, and the investigation is ongoing, Morris said.
CNN's Elwyn Lopez contributed to this report.