Google this week issued an apology for using part of a software application developed by rival in a recently released Chinese software tool of its own.

"We want to face this problem directly and thus apologize to our users and Sohu," Google said in a post on its Chinese-language blog.

Google's apology did not offer an explanation for how part of Sohu's software ended up inside the Google Pinyin Input Method Editor (IME), except to say it was used to develop the software. An earlier statement issued on Sunday acknowledged that "non-Google database resources" were used to develop the Pinyin IME but did not say how it obtained the database.

A Sohu representative could not immediately be reached for comment.

Google's problems began on 4 April when the company released its Pinyin IME, which lets users type Chinese by entering the Pinyin romanization equivalents for characters and words. Shortly after the product's release, Chinese internet users and Sohu engineers noted striking similarities with Google's tool and Sohu's Sogou Pinyin IME.

Pinyin IMEs rely on a dictionary of Chinese words and names, matched with their Pinyin equivalents, to predict which characters a user needs. In the case of Google's IME, the first version of the software contained the names of Sohu engineers, who had put their names in the Sohu dictionary for personal convenience, prompting questions over how the names ended up in Google's software.

Faced with these questions, Google released an updated version of the software on 6 April. That update removed the engineers' names, but did not remove errors inherited from the Sohu software. In one such error, users had to type the wrong Pinyin to get the name of Feng Gong, a Chinese celebrity.

Sohu responded Friday with a demand that Google stop distributing the Pinyin IME based on its dictionary and asked for an apology from the company. Sohu also requested that Google discuss compensation for violating its copyright on the dictionary, and gave the company three days – until Monday – to reply, reserving the right to pursue legal action against Google.

At least two of those conditions have now been met, likely heading off the prospect of legal action.

In addition to the apology, Google issued a further update of its Pinyin IME on Sunday that uses a new dictionary. Sohu confirmed the change on Monday, noting that the similarity between Google's dictionary and its own dictionary had fallen from 96 per cent to 79 per cent.