Washington, Jul 9 (IANS): Asiana Airlines Flight 214 was flying far slower than recommended as it approached San Francisco International Airport just before its crash landing on Saturday, according to preliminary investigations.

Three Indian nationals were among the 305 survivors of the crash that killed two Chinese girls and left 49 seriously hurt. The flight, with 307 people on board, originated in Shanghai and stopped in Seoul.

The Boeing 777 was travelling at approximately 106 knots (122 mph) upon impact and at about 118 knots (136 mph) 16 seconds before impact at an altitude of about 200 feet, the head of the US National Transportation Safety Board said Monday.

The recommended speed upon approach to the runway threshold is 137 knots (157 mph), Deborah Hersman was quoted by CNN as telling reporters.

The onboard systems warned the crew the plane was about to stall four seconds before the crash, she said.

Investigators have found a path of wreckage that started at the seawall and continued to the main wreckage site hundreds of feet up the runway, Hersman added.

The pavement itself was scarred from contact with the landing gear, the engines and the fuselage, she said.

The tail's lower portion was in the rocks at the seawall and "a significant piece of the tail" was in the water, she said.

Additional aircraft parts were visible at low tide. On the path that leads along the pavement away from the seawall were horizontal stabilizers, a vertical stabilizer and an upper portion of the tail cone, she said.

The air-traffic control team found no evidence on voice communications of any distress calls before the accident, she said.

But investigators have found that the pilots had the appropriate charts for the airport and approach in place in the cockpit, she added.

The NTSB was working to find out what the four pilots had done during the 72 hours before the crash in an attempt to determine whether fatigue or sickness may have played a role, she said.

A preliminary review of FAA radar data indicates that there was "no abnormally steep descent curve that's been detected" in the landing approach of the jet, she said, reacting to media reports citing a steeper descent.

And a preliminary review of the engines indicates that both engines were producing power when the plane crashed, she said.