Since U.S.-based sapphire manufacturer GT Advanced Technology’s abrupt bankruptcy announcement last Monday, several law firms have asked investors to step forward.

Law firms including Howard G. Smith, Dunnam & Dunnam, and Johnson & Weaver are investigating whether GTAT had violated federal securities law. Howard G. Smith has especially called out to investors that have lost US $1 million or more to contact the law firm for more information. Those who invested in GTAT prior to the bankruptcy announcement on Oct.6, 2014 are eligible to make claims.

Securities lawyers at Dunham & Dunham are also investigating allegations brought against GTAT, and are encouraging investors that purchased stocks from Nov. 3, 2013 to Oct. 3, 2014 to contact securities attorney Hamilton Lindley at hlindley@dunnamlaw.com.

More than 90 percent of GTAT’s stock value was wiped out last Monday, shortly after the bankruptcy announcement. The company is restructuring company finances at the moment, and has laid-off 890 employees mostly those involved in its sapphire business since. The company is suspected of providing misleading information about its financial situation.