WASHINGTON (AP) -- A top Senate Democrat is asking 30 leading technology, Internet and communications companies to provide detailed descriptions of their operations and human rights practices in China.

Senate Democratic Whip Dick Durbin of Illinois sent letters on Tuesday to technology companies including Apple Inc., Facebook and Twitter seeking information about their business in China and their plans for protecting human rights, free speech and privacy there.

Other companies that received letters include Amazon.com Inc., eBay Inc., AT&T Inc. and Verizon Communications Inc.

Durbin's letter comes nearly three weeks after Google Inc. said it would stop censoring search results in China and threatened to pull out of the country altogether after uncovering a hacking attack that emanated from China and attempts to snoop on dissidents.

Durbin said he is gathering information about the conduct of other big technology companies to prepare for a hearing on Google's actions in China. The hearing will also examine the Global Network Initiative, a voluntary code of conduct for Internet and communications companies that do business in countries that restrict free speech and human rights.

AT&T and Facebook said they would respond to Durbin's letter by the Feb. 19 deadline.

Twitter doesn't have an office in China, but said it will be happy to share its perspective on censorship issues.

Apple said it had no comment. Amazon, eBay, Twitter and Verizon did not immediately respond to requests for comment.