"This is the first time robots like this have ever been used at a major sporting event," Robowatch spokesman Benjamin Stengl said. "They haven't caught anybody. They haven't actually had much to do. This has been a very safe World Cup, luckily."

The outdoor robot OFRO, which starts at $76,000 and resembles a Mars rover on treads, uses thermal cameras at night to spot intruders from their body heat. Similar to ones used by the U.S. military as scouts in

Iraq, the OFRO is capable of far more ¡ª with sensors equipped to detect radiation, toxins, viruses and chemical warfare agents.

"These things won't be used here, but we see this as a learning experience, where we can go back and better the technology," Stengl said. "The robots here will be mostly used where it's very boring or very difficult to see."

The robots get navigation help from the Global Positioning System satellites and send pictures back to a central room in the stadium called the skybox. Through remote control, they can be sent to check out anything suspicious.

A second robot, MOSRO, is shaped like R2-D2 from "Star Wars." The machine, which starts at $15,000, uses mostly video cameras to catch intruders in the parking lots. It also has infrared and ultrasonic sensors.

The robots aren't replacing any humans, just augmenting the patrols.

Robowatch and B.E.S.T., the security company in charge, are discussing using the robots in other places at Olympic Stadium, but Stengl said the locations won't be disclosed if more places are chosen.