Dozens of Iranian scientists and engineers who arrived in the United States last week had their visas revoked upon arrival and were asked to leave the country.
The Iranians, whose visas were approved months ago, were due to attend a meeting in California of the Sharif University of Technology Association (SUTA), a global organisation for alumni of Iran's top scientific university.
SUTA's founding president Fredun Hojabri told SciDev.Net that after a two-month delay for security checks, US consulates had granted visas for about half of the 250 Iranians who had applied.
"But when they arrived at the US airports they were told that their visas had been cancelled and they had entered the country illegally," said Hojabri, a former professor at the University of California in San Diego.
"They were handcuffed, interrogated, mistreated, detained in prison cells and sent back the next day," he said.
The US State Department would not comment specifically on the situation but a spokesperson said visas could be revoked at any time if there are "indications of possibility of ineligibility for admission".
Hojabri believes the decision to revoke the visas was political.
"I am afraid that it was based on the assumption that by humiliating these respected Iranians, they would blame Iran and put the Iranian government under pressure to change its policies," he said.
"But the result was quite the opposite. It gave the Iranian government another justification for its policies toward the United States," says Hojabri.The SUTA meeting was tied to the 100th anniversary of the 1906 San Francisco earthquake and featured presentations about it and recent earthquakes in Iran.