Businessmen from America, the Far and Middle East make up a group of seven different potential buyers.
The takeover could be completed by the middle of November should serious buyers emerge on 7 October.
On Friday, three South African businessmen liked with a possible £300m takeover denied they had any intention to buy the club, with billionaire Johann Rupert saying he had "absolutely no interest and no knowledge".
The South African group were considered to be the frontrunners - with their interest in bringing Keegan back making them popular with the fans. A Nigerian consortium was also believed to have presented its bid of about £350m to the club, but Newcastle refuse to confirm any offer.