(CNN) -- A small plane went down short of an airport in rural Alabama, killing a couple and five of their children, authorities said.
"It's going to take a long time (to investigate) since the wreckage is so deep in the woods," Nick Worrell of the National Transportation Safety Board said Sunday night.
The NTSB and the Federal Aviation Administration are looking into the deadly crash, which occurred Saturday evening near Demopolis, Alabama.
According to preliminary information, the Cessna C421 was flying from St. Louis to Destin, Florida, when it lost its right engine, said the FAA's Kathleen Bergen. The plane was diverted to Demopolis Municipal Airport but crashed about two miles short of the runway, Bergen said.
Seven people were on board the plane, according to Bergen. All seven died.
Marengo County Coroner Stuart Eatmon told CNN the father was the pilot. The wife and at least five children perished in the crash, he said. The bodies were burned "beyond recognition," he said.
Eatmon said it took hours for officials to remove the victims from the plane. The wreckage was discovered around 2 a.m. Sunday, but rescue workers could not remove the bodies for about 12 hours because they had to wait for the plane to cool down. Officials had to use an infrared camera to locate the bodies, he said.
Authorities are waiting to release the names of the victims until family members have been notified.
CNN's Greg Morrison and Stephanie Gallman contributed to this report