The second largest e-commerce retailer in the U.S. is accusing the industry leader of something close to sabotage. Auction site eBay on Wednesday claimed that Amazon employees were using eBay’s own web infrastructure to convince eBay sellers to move over to Amazon, the Wall Street Journal reported.

A company investigation by eBay found that around 50 purported employees of Amazon got in touch with eBay merchants, trying to bring them over to Amazon. There were more than 1,000 messages sent in total through eBay’s online messaging feature. A seller reportedly told eBay about the attempted contact in late September, prompting the investigation.

The Amazon employees used tactics to get past eBay’s moderation, according to CNBC. Misspelling the word “Amazon,” asking to meet in-person and other common strategies were utilized by those attempting to coerce eBay sellers to cross to the other side.

If the allegations are true, Amazon could be in violation of California’s Comprehensive Computer Data Access and Fraud Act. The law protects individuals and businesses from “tampering, interference, damage, and unauthorized access to lawfully created computer data and computer systems.”

“We have demanded that Amazon end its unlawful activity and we will take the appropriate steps, as needed, to protect eBay,” eBay said in a statement on Wednesday.

There did not appear to be comprehensive legal action over the alleged practice, but eBay said it sent Amazon a cease-and-desist letter earlier this week. Amazon, for its part, said it would investigation eBay’s accusations.

Both Amazon and eBay own a large share of the online retail space, but eBay may feel like it is being picked on by a more powerful entity in this situation. Data from eMarketer earlier this year found that Amazon dominated U.S. online retail sales with 49.1 percent market share. On the other hand, eBay was in second place, with just 6.6 percent.

Third-party sellers are a massive part of both companies’ business models. Last month, Amazon launched an online storefront dedicated to “small and medium” businesses that sell on the site. In the announcement, Amazon said around 50 percent of everything sold on the site came from third-party sellers.