Undated handout photo of the Beyond Meat burger. REUTERS/Beyond Meat/Handout

(Reuters) - Tyson Foods TSN.N, the largest U.S. meat processor, said on Thursday it slightly raised its stake in plant-based protein maker Beyond Meat as it looks to tap growing demand for alternative sources of protein.

The company, which already owns a 5 percent stake in Beyond Meat, said it participated in the most recent funding round through its venture capital fund. Details of the investment were not disclosed.

California-based Beyond Meat sells plant-based burger patties, heat-and-eat meals and non-GMO soy and pea protein frozen foods at grocery chains such as Amazon.com Inc's AMZN.O Whole Foods Market, Publix and Albertsons Cos Inc's ABS.N Safeway.

Traditional meat sales have come under pressure on growing concerns about animal welfare and the environmental impact of intensive animal farming, apart from a rising perception of vegetarian meals as healthier.

U.S. companies such as Beyond Meat and MorningStar Farms, owned by the world's largest cereal maker, Kellogg Co K.N, are leading the charge in the meat substitute market.

The industry could reap $5.2 billion in sales by 2020, according to Oregon-based Allied Market Research (AMR), an 8.4 percent rise from 2015.