Four people were killed Wednesday when a small Piper aircraft crashed into shallow waters near the remote coastal town of Seldovia, Alaska, authorities said.

The Piper PA-24 had departed from Anchorage and was flying toward Seldovia Airport, located about 136 miles (219 kilometers) southwest of Anchorage, when it went down in the Seldovia Slough near the shoreline.

The aircraft came to rest fully submerged in approximately 15 feet (4.6 meters) of water, according to Clint Johnson, the Alaska region chief of the National Transportation Safety Board (NTSB).

Alaska State Troopers and other emergency personnel responded to the crash after authorities were alerted Wednesday afternoon.

Because the aircraft was submerged and the tide initially prevented responders from reaching the wreckage, troopers had to wait for the water level to recede before accessing the plane.

Authorities subsequently recovered the bodies of all four adults aboard. The remains were transferred to the state medical examiner's office, while officials said the identities of the victims would not be released until their relatives had been notified.

The cause of the crash remains unknown.

The NTSB has opened an investigation into the accident and is expected to examine the aircraft, flight conditions and circumstances surrounding the final stage of the flight. No specific mechanical failure, weather condition or pilot error has been identified publicly as a cause.

The Seldovia accident comes less than a week after another deadly aviation accident in western Alaska.

On August 20, a Cessna 441 operated by Security Aviation crashed near the remote Cape Newenham Long Range Radar Site, killing all eight people aboard.

Investigators said the aircraft had encountered rapidly deteriorating visibility while attempting to land. During a subsequent approach, visibility fell to less than a quarter-mile in heavy fog, and the pilots were unable to see the gravel runway before the aircraft crashed.

The two crashes are being investigated separately, but the incidents have renewed attention to aviation safety in Alaska, where remote communities often depend heavily on small aircraft for transportation.

Alaska's challenging terrain, rapidly changing weather and the large number of remote airstrips can create particularly demanding conditions for pilots.

Alaska Sen. Dan Sullivan said he would receive briefings from the NTSB and the Federal Aviation Administration as investigators work to determine what caused the Seldovia crash.

The investigation is expected to examine the aircraft's maintenance and operating history, the pilot's qualifications, weather and flight conditions, and evidence recovered from the submerged wreckage.

For now, authorities have not identified a probable cause.

The names of the four victims will remain undisclosed until next-of-kin notifications are completed, while investigators continue working to establish what happened during the flight from Anchorage to Seldovia. (ILKHA)