Here's a curly one to add to the pot, was received from an apparently reliable overseas source as being a direct quote of a conversation with someone from the airport;
"He called mayday prior to rotation and then again early upwind. We suspect he lost an engine for the first mayday and then lost the second engine. It has more than enough power to continue on climb on a single engine so it must've been a double failure or something else catastrophic. Fuel would be the first suspect for losing two engines. The video I saw before he crashed he was traveling very slow, almost gliding. "
I have no way of verifying the conversation and it doesn't make much sense to me that the pilot would have called mayday on the runway and continued with the take-off, but there you have it.