Nearly a dozen media companies including The Washington Post, Dow Jones and the Associated Press sent a cease-and-desist letter to e-reader application Zite on Wednesday, saying the company’s practice of reusing and aggregating their content infringes their copyrights.

Zite describes itself as a free personalized magazine for the iPad tablet computer. Earlier this month, it said it received 100,000 downloads of its app in its first week.

The media companies said Zite’s reproduction of images, news stories, essays and other content was done without permission and “adversely impacts our businesses.”

“Your application takes the intellectual property of our companies, as well as the hard and sometimes dangerous work of tens of thousands of people. It deprives our websites of traffic and advertising revenue,” the media firms wrote.

The letter comes amid a rush to put media content on e-readers and tablet computers such as the Kindle and iPad as strapped newspapers and magazines seek new sources of money to replace lost revenues from declining print advertising and classified listings.

But publishers have been at odds with technology companies over partnerships and revenue deals. Apple’s 30 percent cut of in-app purchases was a source of contention between the iPad-maker and media firms. Apple insists on 30 percent of revenues from money made through apps on its iPhone and iPad.

The other media companies that signed the letter are Advance Publications, Gannett, Getty Images, McClatchy, National Geographic Society, Scripps, Time and Slate.

Zite did not respond to a request for comment.

The New York Times, USA Today and The Washington Post have joined together with some aggregation sites such as Ongo to create subscription-based models for their news.

Media organizations have pursued various approaches to making money online. For example, the New York Times, Financial Times and Wall Street Journal put some of their content behind “paywalls,” which provide access to unlimited content to paying subscribers.