The man wearing khaki pants and a ball cap probably blended in at the Houston offices of a major energy company as he casually walked around in the early-morning hours with a backpack and shoulder bag.

But FBI agents said Monday that he apparently wasn't an employee or contractor at the time, but rather a criminal who made off with corporate secrets that could be in the hands of a competitor or foreign government.

Agents are appealing to the public for help in identifying the man as part of their hunt for answers in the brazen foray last year.

And they have a warning for the Oil Patch: economic espionage and trade-secret thefts against U.S. oil and natural gas companies are on the rise.

"The financial downshift of companies leads the bureau to assess that there is more of a vulnerability for potential insider threats or economic espionage on behalf of foreign adversaries or governments," FBI Special Agent Michael Morgan said.

What looks like petty theft - such as someone breaking into a building and walking out with a handbag - could feed into the $400 billion a year lost by U.S. companies to foreign competitors due to targeted thefts and espionage, he said.

The man with the backpack was a throwback to old-school security concerns as he literally walked in and out of the company, rather than being part of a cyberattack, which in recent years has taken center stage.

"What we are hoping is that in his world now he not only has the FBI looking for him, but a population of a couple of a million people who have become eyes and ears for us and may recognize this individual and be able to come forth with information," Morgan said.

The company has asked authorities not to identify it publicly, FBI officials said. Revelations that intellectual property has been compromised pose security concerns and also could impact stock prices, experts said.

Economic espionage involves theft of a proprietary product, process or idea for the benefit of a foreign government, including state-owned companies. It is a federal crime that carries a sentence of up to 15 years in prison and millions of dollars in fines. China has been a major offender, according to officials.

Fortune 500 company

Trade secrets related to the search for crude oil beneath the land and sea and to the refining of oil into gasoline are of particular interest when foreign entities target U.S. companies, universities, think tanks and researchers, according to the FBI.

In the Houston case, the unidentified man made two early-morning visits to the Fortune 500 company in 2015, and was apparently never challenged by security or other employees. Both times he wore khaki pants and a baseball cap.

On June 25, 2015, he got into a building at 3 a.m. through a door that wasn't properly locking. He wandered for two hours before leaving with company and employee property, including the backpack and a shoulder bag, which appeared to be full.

On Dec. 30, 2015, at about 5 a.m., the same man tried to get into the same building but was unable to reach employee offices. He instead grabbed a security radio from what appears to be a lobby security area as he left.

Authorities won't specify what type of intellectual property was stolen but say it can traditionally include materials such as printed books, laptops and flash drives.

When in doubt, call security

Retired FBI agent Rich Garcia said cases have shown over and over that people such as employees in a business don't like to question people they don't know, even in their own workplace.

"He dresses or carries himself so he looks legitimate," Garcia said. "People have a tendency not to get involved and not challenge. They don't want to be bothered by the issues, don't want to offend somebody, don't want to get hurt."

He suggested that people who don't want to confront a stranger should at least contact a company official or security.

"If you feel something is not right, it is probably not right," he said.

David H. Laufman, chief of the Counterintelligence and Export Control Section at the Department of Justice, warned during a closed-door conference here in May that U.S. corporations' secrets aren't just facing threats from foreign companies but also governments. He cautioned corporate executives to safeguard their companies.

"Identify what you deem to be your crown jewels and implement tiered security efforts to protect them," he told them.

As for the man in the video, he is described by the FBI as being white, about 35 to 45 years old and approximately 5 feet, 10 inches tall. They also said he had a noticeable twitching to his upper body, head, neck, shoulder and arms, which is visible in surveillance video.

Crime Stoppers is offering a reward of up to $5,000 in the case. Anyone who has information about the theft is asked to contact Crime Stoppers at 713-222-8477 or at www.crime-stoppers.org.