After two years of collaborating on self-driving cars, BMW and Chinese search giant Baidu have ended their partnership, according to multiple reports. Baidu is said to now be searching for a new automaker to team up with as it looks to ramp up its testing of autonomous vehicles in the US.

Wang Jing, the head of autonomous car development at Baidu, told Reuters the company was now using cars from Ford's Lincoln in its US testing. "I'm open for any partners, actually I'm talking to many,” Wang said.

Spokespersons for Baidu and BMW declined to comment, but a BMW executive told Reuters that the two companies differed on the direction of their research into autonomous vehicles. "We now have found that the development pace and the ideas of the two companies are a little different," BMW's China CEO Olaf Kastner said.

BMW has said it wants to bring a self-driving car to market by 2021. Baidu was more ambitious, aiming for 2018. There were other signs that the two companies weren’t entirely in lockstep. BMW had forged partnerships with other companies working on autonomous technology, including collision-avoidance detection firm Mobileye and chip-maker Intel.

BMW and Baidu first began collaborating in 2014. At the time, Baidu senior vice president Wang Jin said that his company would launch of a new self-driving car with the German car manufacturer by the following year. The prototype vehicle would be used to test Baidu's autonomous technology, but would still have a human driver present.

That vehicle never materialized. But earlier this year, Baidu received an autonomous vehicle testing permit from California’s Department of Motor Vehicles, bringing the Chinese search giant one step closer to testing its self-driving cars on Google’s home turf. The Chinese search company has also been staffing up in Silicon Valley, building up a team of at least 100 engineers.