Western Digital Corp.'s  (WDC) - Get Report bitter spat with its flash memory joint venture partner Toshiba Corp. (TOSYY) just got a whole lot worse. 

The Japanese company is blocking some Western Digital employees' access to shared databases and, in certain instances, to the JV facilities themselves, Western Digital said Thursday, June 29.

"This action will have the consequence of harming not only Toshiba's stakeholders, but also our respective customers," according to a statement.

Toshiba stock fell 3.7% Thursday to close at ¥277 ($2.46) per share. Western Digital stock ended Wednesday at $93.67, up 2.5% on the day, and traded marginally higher in the after hours market.

The claim comes a day after Toshiba said it had filed to sue Western Digital for ¥120 billion ($1 billion), alleging that the San Jose, Calif. chip maker had illegally interfered in the sale of Toshiba's memory chip business. It also claimed that Western Digital employees had stolen proprietary information from the JV and said it will block Western Digital employees from accessing sensitive information.

Tokyo-based Toshiba, last week, named a Bain Capital LLC-led consortium as its preferred bidder following an auction of its Toshiba Memory Corp. business. Bain, backed by South Korean chipmaker SK Hynix Inc. and Japanese state-backed investors Innovation Network Corp. of Japan and Development Bank of Japan, offered about ¥2 trillion ($18 billion) for the world's biggest maker of NAND flash memory.

Toshiba on Wednesday missed a self-imposed deadline to finalize the terms of that deal.

The Japanese firm's filing was a tit-for-tat response to Western Digital's request for an injunction on the sale of Toshiba Memory Corp., which includes the NAND JV that is part owned by Western Digital's SanDisk subsidiary. The injunction, if upheld, could block a sale of the until an arbitration hearing, which Western Digital expects will support its claim that the unit can't be sold without its consent.

"We believe the actions taken by Toshiba are continued attempts to both pressure Western Digital to relinquish its previously agreed upon and legitimate consent rights, and to distract Toshiba's stakeholders following its annual general meeting," said Western Digital. "It is surprising that Toshiba would take such actions given the implications for its employees, customers, shareholders and creditors."

The San Jose, Calif. chip maker declined to comment Toshiba's filing, made in a Tokyo District Court, claiming that it had not received no information on the case.

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