By Paulo Prada and Pedro Fonseca

RIO DE JANEIRO (Reuters) - Security is the top focus for the laboratory that will conduct doping exams at the upcoming Olympics in Rio de Janeiro, the lab's director said Friday, amid global scrutiny following the recent scandal surrounding Russian athletes.

Citing major breaches that the World Anti-Doping Agency (WADA) described at a Russian laboratory, chemist Francisco Radler said the lab must ensure that cheating, through infiltration by outsiders or other efforts to manipulate testing, is "impossible."

In an interview with Reuters outside the new laboratory, a remote five-story building on the island campus of the Federal University of Rio de Janeiro, Radler said a security force of about 50 people, including military police and private guards, will guard the nearly 200 local and international scientists and technicians who will conduct Olympic testing.

He said the laboratory, following a brief suspension because of implementation problems with new equipment, is fully operational and ready for testing once the Games begin on Aug. 5.

Given the hardware and know-how that will be on hand for the Olympics, after an investment of about 190 million reais ($58.6 million) by Brazil's federal government, Radler says the lab's goal is not just to show technical proficiency but to prove that it can safeguard the integrity of testing.

"Concerns with security, with access to samples, with the people who come in and out of this complex, are infinitely greater," he said.

So stringent is security that Radler spoke with Reuters outside a metal fence delineating a perimeter more than 100 meters from the building itself. Two hundred cameras monitor the lab and guards early Friday inspected even the trunks of employee cars as they pulled through a checkpoint.

In Russia, following revelations by a whistleblower from the country's own track and field team, investigators learned of security flaws that included even a small hole in a lab wall through which staff secretly took test samples and swapped them with clean substitutes.

The Rio facility, officially known as the Brazilian Laboratory for Doping Control, will test for more than 500 banned substances from about 6,000 fluid samples taken from athletes over the course of the Games. The number of tests at the 2012 London Olympics totaled about 5,000.

EVER-CHANGING DOPING CHALLENGES

Aside from a greater volume of samples, Radler said the lab must contend with an ever-changing game of cat and mouse between doping agencies and athletes and coaches who seek to elude detection of performance enhancing drugs.

Compared with anabolic steroids and other well-known substances, newer challenges include the use of proteins that trigger the release of growth hormones. Scientists are also studying so-called gene doping, whereby an athlete could in theory use a virus or other agent to prompt a genetic change that would enhance performance.

"The tendency is always for athletes to move toward techniques that laboratories may not yet be fully prepared for," he said, noting that it remains unclear if some techniques, like gene doping, have ever successfully been used.

In addition to about 80 of the laboratory's own staff, who will remain with the university once the Olympics are over, more than 100 other doping officials will help conduct tests during the Games.

They will also freeze samples, kept by the International Olympic Committee, so that future testing will be possible as technology advances.

"The best possible team that could exist will be here," Radler said, minimizing the technical issue that in June led to a brief suspension by WADA of the laboratory.

The suspension, which came after the laboratory itself notified WADA of a problem, had to do with fully getting the facility up to speed with some of the 50 million reais worth of new equipment brought in since it began ramping up operations in 2014, Radler explained.

When WADA lifted the suspension this month, it said testing "has been robust throughout the laboratory's suspension and it will also be during the Games."

Radler dismissed concerns that the large investment in equipment will have been spent on resources no longer useful after the Olympics.

University and government officials, he said, will evaluate demand for doping tests in Brazil after the Games and, if necessary, redistribute some of the equipment to other universities, where it could be used for research and educational purposes.

(Editing by Daniel Flynn and Mary Milliken)