Loud engine noise continue after key was pulled

Desperately need help!!

Yesterday, I drove my 99 RX300AWD (odo=110K miles) for 20 Miles with A/C off.

Then, I parked the car for 2 hours.

When I started the engine, there was a loud noise along with engine noise (sort of crane noise)

Then, I shut the ignition off & pulled the key, engine shut off.
However, that strange noise continue for approx 30 second (enough time for me to open the hood and trunk trying to get a wrench)

Then, the noise completely gone by itself.

I started the engine again & no more noise. I tried several times, and couldn't repeat the problem.

Later, I drove the car for 100 miles, with a/c on & off. Nothing unusual.

Trans oil&Engine oil level is fine.

Could it be the starter keep engaging to the flywheel, or starter relay? If yes, why the noise continued for 30 sec after the key was pulled?

Appreciate any suggestion.
Email: mek88@yahoo.com
Los Angeles

 

Could it have been something hitting the thermostatically controlled radiator fan. These will run after the key is shut off sometimes. Posiibly something got sucked into it and dropped out after the fan shut off.
Oliver