New Delhi, Sep 23 - A US probe has found that the pilot and co-pilot of the chopper that crashed in an Andhra Pradesh forest, killing chief minister Y.S. Rajasekhara Reddy, early this month knew they were flying in a dangerously bad weather, an official said here Wednesday.

'The US FAA (Federal Aviation Administration) investigated the conversation between the pilot and co-pilot minutes before the chopper crashed. They also spoke of bad weather,' said the senior official of the civil aviation ministry.

The Indian government had sent cockpit voice recorder and some samples of the wreckage of the twin-engine Bell-430 chopper to the US authority for investigation.

The chopper crashed Sep 2 in Nallamala forests, about 70 km east of Kurnool in Andhra Pradesh. The chief minister, two officials and the two pilots were killed in the crash.