MIAMI — A scientist detained at Miami International Airport because of a suspicious item in his luggage had once been charged with illegally transporting bubonic plague, a senior law enforcement official said.

No dangerous material was found on 70-year-old Thomas Butler after he was detained Thursday night, the official told The Associated Press on Friday. Butler had been acquitted of the charges of transporting the potentially deadly germ in 2003.

Butler cooperated fully after he arrived on a flight from the Middle East, said the official, who requested anonymity because he wasn’t authorized to release the information.

Most of the airport was shut down Thursday night after officials found a suspicious metal canister in Butler’s luggage. A Homeland Security spokesman said at first it looked like a pipe bomb, but no explosives were found.

The senior law enforcement official told the AP that a Transportation Safety Administration inspector noticed an odd container as Butler was going through Customs after arriving on a flight from the Middle East, where he had been teaching at a Saudi Arabian university.

Those facts caused the inspector to run Butler’s name in a database and discover that he had been tried on the plague charges in 2003. Officials decided to evacuate the airport and detain Butler.

Tests showed that Butler, the container and his other belongings did not contain any hazardous biological material or explosives. He was released Friday morning. No one answered the door at an address in Lubbock, Texas, listed as his on a U.S. Department of Commerce website.

A Miami-Dade police bomb squad spent hours scouring the airport. Between 100 and 200 passengers were evacuated from four of the airport’s six concourses. Airport roadways and a hotel near the airport’s international terminal were closed down. Police and airport officials described the shutdown of the concourses as a public safety precaution.

Butler is a professor at Ross University in Dominica on a teaching assignment in Saudi Arabia, said another government official who also requested anonymity to discuss the ongoing investigation.

In 2003, the world-renowned plague researcher prompted a bioterrorism scare when he reported that 30 vials of plague samples possibly had been stolen from his Texas Tech lab. Within hours, dozens of federal agents swarmed to Lubbock.

A frantic search for the vials ended when Butler gave FBI agents a written statement in which he admitted a “misjudgment” in not telling his supervisor that the vials had been “accidentally destroyed,” according to court records.

Before Butler’s trial, leading scientific organizations expressed concern about the criminal case against him and its effect on infectious disease research. Four Nobel laureates said in an open letter that Butler had been “subjected to unfair and disproportionate treatment” and that prosecuting his case “is having a negative impact on the future of research in this crucial national-security-related field.”

Butler testified that FBI agents forced him to make the admission to calm the public’s fears.

He was acquitted of the most serious charges of smuggling and illegally transporting the potentially deadly germ, and of lying to federal agents about the missing vials.

Jurors found Butler guilty of the mislabeling and unauthorized export of a FedEx package that contained plague samples he sent to Tanzania. An appeals court upheld his convictions and the U.S. Supreme Court declined to review the case.

Butler served two years in prison and he was on supervised release until 2008. He also agreed to retire from the university and to surrender his medical license.

He is not currently licensed in Texas, a spokeswoman for the Texas Medical Board said Friday.

Passengers, workers and others were allowed back in just as the airport was expecting the first of 1,500 passengers on flights between 4 a.m. and 6 a.m. alone — and more thereafter.

“Everything’s back to normal,” airport spokesman Greg Chin told the AP.

Lennox Lewis, was waiting to fly to Barbados later Friday morning in one of the four concourses that had been closed.

He said the Miami airport is “one of the most stringent” to get through because he has to be fingerprinted and have his picture taken at customs.

“Traveling right now is a pain but you have to do it,” said 39-year-old Lewis, who was flying with his two small children after a trip to North Carolina and Disney World. “I don’t get overly worried that people will do stupid things.”