Revelers play in tomato pulp after the annual "La Tomatina" (tomato fight) in Buñol, near Valencia, Spain, Aug. 26, 2015. REUTERS/Heino Kalis

It’s the last Wednesday in August, and it’s time for Spain’s annual La Tomatina festival — a “fight” that uses tomatoes as ammunition, with largely tourists making up most of the fighters.

The festival, now in its 71st year, got underway at 11 a.m. local time (5 a.m. EDT) in the city of Buñol in Valencia province, near Spain’s eastern coast. Over 330,000 pounds of tomatoes were transported to the town in preparation for the festival, and all 20,000 tickets were sold out.

The organizers are streaming the hour-long event live, and it can be viewed here.

Rules for participation, if you already have a ticket, are few and simple. No hard objects should be thrown, in order to avoid injuries to others. As such, things like backpacks, cameras and such are not allowed. Participants are advised to also squash the tomatoes before throwing them. And the organizers ask you to not tear and throw your own clothes, or those of others. Wearing goggles is a good idea.

The festival traces its history to an actual fight in August 1945 that, as a matter of chance, involved people pelting each other with vegetable and fruits, including tomatoes. Over the years, the festival became more organized, was temporarily banned (participants once held a “funeral” for a tomato instead), and in 2002, included in Spain’s official tourism circuit.

The number of participants in the festival, held in a narrow street in Buñol, has been as high as 50,000, compared with the town’s population of less than 10,000. However, for safety reasons and to better manage the festivities, only 20,000 people are allowed to join in the fight since 2013.

Shopkeepers along the festival street cover their shop-fronts with sheets of plastic to keep out the mess. After the fighting is over, large hoses wash down both the participants and the street. This year, security around the event is tight too, given the recent terror attacks to have struck Europe.