SPB.N NEWS – Online Desk: The Japanese industrial giant has now had more than 40% of its value wiped off since 26 December.
It comes after the firm warned that its US nuclear business may be worth less than previously thought.
Shares were down 26% at one stage in Tokyo, but were trading 15% down in afternoon.
Toshiba stocks had already lost 20% on Wednesday and 12% on Tuesday.
Why are Toshiba shares tanking?
Most people still recognise the name Toshiba for its electrical products, but it is a very diverse conglomerate.
And these latest problems stem from its nuclear services business which brings in about a third of its revenue.
Toshiba said on Wednesday that it faced a possible heavy one-off loss, linked to a deal done by its US subsidiary, Westinghouse Electric.
Westinghouse bought a nuclear construction and services business from Chicago Bridge & Iron in 2015. But assets that took on are likely to be worth less than initially thought – and there is also a dispute about payments that are due.